Like any other specialized field, the world of commercial doors has its own technical lingo, which may be opaque to those not in the business. For your enlightenment and edification, we here share definitions for a few of the more common terms relating to doors and door hardware.

Active leaf

In a set of double doors, the door, or leaf, of the two that is opened first, and that has the locking mechanism. The other door is, as you might expect, called the inactive leaf, and is usually held closed by top and bottom bolts.

Continuous hinge

Also known as a piano hinge, this is a hinge that runs the full length of the door from top to bottom.


In a keyed door lock, the part that contains the tumbler mechanism and the keyway into which the key is inserted.


A heavy-duty lock that instead of being spring-activated is operated by a key or a turnkey, which slides a metal bolt from inside the door into the jamb.

Door clearance

This is the amount of space between the door and its frame, between the door and the floor, or between the edges of double doors where they meet

Door closer

A mechanism that closes a door automatically, after it has been opened mechanically or manually.

Exit device

Popularly known as a panic bar, this is a door-locking device that allows quick exit when you push on a cross bar to release the door latch.


This refers to the surface of the door that you can see when the door is closed.

Fire rated door (or frame)

This is a door or frame that has been tested for its fire resistance, and assigned a rating for how many minutes it can withstand exposure to fire before it combusts. It may also be rated for how well it resists transmitting heat.


The hand or handing of a door is the direction in which it swings open – doors are either left- or right-handed. If you’re looking at the door from the outside and the hinges are on the right side, it’s a right-handed door; if they’re on the left, it’s left-handed.


The door frame to which the door’s hinges are attached, the jamb is what surrounds the door when it’s closed. The jamb depth is the width of the door frame if you were looking at it from the side – i.e., its width from the front side of the door to the back. Jamb depth is close to but not the same as wall thickness; when choosing a door frame you should always make clear which one you’re talking about.

Kick plate

A plate mounted on the lower part of a door to protect it from damage and scuffing.


A vertical post in a door opening, typically between two double doors. A mullion can be permanent or removable.

These are only a few of the sometimes arcane terms familiar to commercial door professionals. Don’t think you need to master the lingo in order to talk to us at Sacs Door & Gate Corp. – we make it our business to understand our customers’ needs even if they don’t speak commercial door. But if you want to learn more, check out this glossary.