During the past several years, building security for residences and businesses has become an expanding topic. Consumers are demanding improved protection from potential intruders and extreme weather conditions. Door manufacturers are responding by focusing on the locking hardware for their products. While many hardware systems inspire the confidence consumers seek, few non-electrical security products change opinions as dramatically as multiple locking door hardware (MLDH) systems.
What is MLDH?
By definition, MLDH is any system featuring multiple locking point
interactions (between door and frame) at various perimeter locations. Despite a recent
re-emergence in the United States, MLDH has remained popular in Europe throughout the
years. The term “re-emergence” applies to the U.S. market because many current
MLDH systems resemble the old, surface-mounted cremone and slide-bolt systems used on
American-made doors during the 1800s. It seems likely that these early locks were either
spawned from European designs or brought over directly.
At some point, U.S. consumers changed their attitude toward such locks and abandoned
further use and development. MLDH virtually was unchanged and unpromoted in the United
States for more than 100 years. Single-point latches and deadbolts became the more common
hardware—offering simpler and more cost-effective choices. Concurrently in Europe,
however, existing MLDH designs continued to be enhanced and improved. Perpetual
development is a clear and defining factor between modern MLDH as a European versus
American product.
In Europe, a breakthrough in MLDH design was achieved when the first centrally-operated
systems were introduced about 30 years ago. Centrally-operated systems meant all points of
the system would be engaged and disengaged with one lever action. The entire system could
be locked with a cylinder. Prior to this development, MLDH was a collection of
individually-operated hardware pieces that together comprised the system. Now, all locking
points are a complete system.
The modern MLDH system was born.
Centrally-operated MLDH systems were introduced initially to improve the water, air and
wind tightness of wood doors. Success was accomplished easily even with the most basic
designs—numerous roller pins along the vertical edge. But it was the introduction and
rise of uPVC doors that gave MLDH technology its greatest push. Doors made of uPVC
materials are not as rigid as wood doors and are susceptible to flexing under wind loads
and pressure changes. Over time, the doors warp. With protection from weather, and now
door flatness to consider, MLDH designs began featuring locking points at the top and
bottom to complement those already along the vertical edge. These top and bottom locking
points helped maintain door stability by keeping the corners and horizontal edges tight
and flat against the jamb stop. Also, the addition of top and bottom locking points added
a level of security that manufacturers eventually would use to promote MLDH to global
markets.
Security was not a major concern in Europe and MLDH designs were not influenced by the
need for high security. Therefore, most MLDH did not incorporate deadbolts. Some current
European models still do not. As crime rates increased, security became a serious
consideration in the MLDH used for entry doors. Simultaneously, two MLDH concepts
evolved—patio doors and security doors. Patio door hardware continued to be
manufactured with rolling pin locking points—varying and increasing the perimeter
locations. Security door hardware for main entry doors, however, began featuring deadbolts
with a minimum of three locking points. The popularity of MLDH spread across Europe and
Asia. Interestingly, each market and door application began identifying its own specific
needs. MLDH designs became different as each manufacturer created unique features and
designed models to provide specific benefits.
Coming to America
No more than 15 years ago, modern MLDH systems made their first appearance
in the United States. Mass-produced, wood patio double doors were the first American-made
products introduced with centrally-operated MLDH. Despite weather-resistance, door
stability, intrusion security and convenience benefits beyond the capabilities of manually
operated, individual locks, MLDH did not gain immediate acceptance with U.S. consumers.
Many viewed MLDH as an expensive, complex and unproven substitute for hardware that was
familiar and dependable. But door manufacturers (mass producers and custom) realized MLDH
could improve their product marketability for both patio and entry doors significantly.
Consumers concluded that an investment in a high-quality door should be protected with the
most advanced, secure locking hardware available. A sweeping move to MLDH on doors was
inevitable.
As MLDH became popular in the United States, manufacturers began developing more doors
with MLDH as standard equipment. As use increased, European manufacturers redesigned MLDH
systems with added features.
These enhancements included:
• Introduction of new bolt configurations (e.g., hook bolts, horn
bolts, flipper bolts, etc.);
• Deadbolts with more throw distance (3/4- to 1-inch);
• 90 degree key/thumbturn lock functions instead of the 180
degree-plus previously required with standard profile cylinders; and
• Custom-powder-coated and plated faceplate finishes to meet
aesthetic desires.
Within the past ten years, several U.S. door manufacturers had developed relationships
with Europe’s established MLDH manufacturers through distributors transplanted into
the United States. MLDH businesses grew slowly but steadily as new construction and
remodeling surges brought increased door sales. As a result, U.S. door manufacturers
sought more unique and convenient features from the MLDH being used on their doors.
New revolutions in the MLDH designs were stagnant as European manufacturers absorbed the
request made by U.S. consumers. Manufacturers had to consider global concerns as well,
since MLDH was still extensively used outside of the United States. But, once introduced,
the changes represented remarkable advancements that offered new levels of security and
convenience. Despite these significant improvements, most of these features were not
available to markets outside of North America. The needs and applications of MLDH differed
regionally (i.e., North America, South America, Europe, Africa, etc.). These new MLDH
systems were completely different from any previous versions and had gained identity as an
American product. Some examples of these “Americanized” upgrades were:
• Deadbolt located above the operating levers. Previously, the
levers were located above the deadbolt;
• “Nightlatch” type (aka semi-automatic) functions
allowing deadbolts to be engaged merely by turning the key or thumbturn. Previously, all
locking points (including deadbolts) were engaged by the lifting lever;
• Spring-loaded shoot bolts that allow systems to be locked even if
the shoots are not fully engaged. Previously, shoot bolts had to be fully engaged for the
system to be locked; and
The refinement of automatic locking systems that instantly and automatically engage the
locking points when the door makes contact with the frame. Previous attempts at automatic
MLDH proved difficult to install, adjust and service, with a generally unreliable service
life.
Building Ordinances and the Need for MLDH
Increases in new construction and remodeling projects were not the only
factors contributing to the rise of MLDH in the United States. Special building ordinances
and ratings, namely the California Model Building Security Ordinance (CMBSO) and hurricane
codes in Dade County, FL, were also influential.
The CMBSO began as a local construction ordinance in Orange County, CA. A crime prevention
task force, in conjunction with Orange County police, initiated and furthered development.
The ordinance was intended to improve the forced entry prevention capabilities of exterior
door and windows by establishing standard requirements.
Compliance to CMBSO was (and is) the responsibility of the project architect and door
manufacturer. One method used to meet such requirements incorporates hardware systems with
multiple locks on doors. Since multiple locking points afford additional security, this
method increased the likelihood that a manufacturer’s product would meet the minimum
requirements for compliance.
CMBSO is a local ordinance that has gained broad exposure. Although it is not related to
California’s building codes, it is estimated that approximately 85 percent of
localities in California comply. Whether all doors meeting the compliance requirements
used MLDH is unknown. Certainly, though, MLDH has gained increased exposure as a result.
Yet another example of a building ordinance that has contributed to the increased
popularity of MLDH has been the hurricane approval rating of Dade County. Developed to
establish guidelines for doors and windows that must withstand hurricane conditions, Dade
County had worked closely with the American Architectural Manufacturers Association (AAMA)
to create compliance testing and approval standards. Manufacturers seeking an approval
rating for doors are required to submit a complete product for laboratory testing.
A complete door product consists of the sash and frame with locking
hardware installed. The most extensive and rigorous hurricane testing consists of several
qualification areas for structural integrity including air/water infiltration, cycles,
forced entry and missile impact. Each product that complies with Dade County compliance
must be tested and approved separately—even if there are only slight differences.
MLDH systems have been used on doors that have achieved Dade County’s approval
rating. This is not to imply that only MLDH will allow a door to pass such testing, but it
seems that MLDH increases the probability. This is obvious when considering the missile
impact test that requires the launch of a projectile to contact a closed door at various
locations. Successful passage of the test requires the door to remain closed during impact
and prevail completely functional. With the top and bottom corners opposite the hinge side
among the locations directly impacted, locking points at the corners may improve
performance. Door manufacturers understandably are reluctant to share designs that have
successfully passed the Dade County testing. Nevertheless, as more manufactures seek to
gain Dade County approval ratings for their products, more MLDH systems will be
contemplated and used.
Conclusion
Undoubtedly, the popularity and needs of CMBSO and Dade County approval system will affect
MLDH in the future. So will the newer, upgraded lock varieties, as more appealing options
are available. As more architects and millwork shops design custom doors, more MLDH will
be specified to maintain the stability and security. Additionally, as more manufacturers
incorporate MLDH into their products, more end-use consumers will be enlightened to the
benefits and features.
In the United States, MLDH systems will probably never out-sell the standard latches and
deadbolts; yet growth in this area is expected to continue. Presently, not everyone is
familiar with MLDH. Perhaps this is part of the reason MLDH had not attained the same
level of prevalence as in Europe and other regions. Soon, though, every American will at
least recognize hardware with multiple locking points. Once that happens, we can begin to
ask, “What’s your point?”
John Imbriale is customer service supervisor for G-U Hardware, based in Newport News,
VA. This article was reprinted with permission from Doors and Hardware magazine, published
by the Door and Hardware Institute, 14150 Newbrook Dr., Suite 200, Chantilly, VA 20151;
703/222-2010; www.dhi.com
USG
© Copyright 1999 Key Communications, Inc. All rights reserved. No reproduction of any type without expressed written permission.