DOOR BLOK XL
There are two kinds of doors on which the original DOOR BLOK won't work: doors with latch guards and doors with panic bars.
Doors With Latch Guards
Latch guards, or theft plates, are designed to prevent someone from popping the lock with a knife or screwdriver. The plate covers the gap between the door and the jam and prevents access to the latch mechanism.
Here's a picture of a door that has a latch guard bolted to it. The view from the inside of the door (below right) clearly shows how much the latch guard overlaps the edge of the door.
For these types of doors, you're going to need to use DOOR BLOK XL. Although it's only an inch longer than the original version, that extra little bit of rubber enables it to be hooked to the inside knob/handle, wrap around the latch guard, and then hook over the outside knob/handle.
Doors With Panic Bars
Here's a picture of a classroom door that has a panic bar, or push bar, as the inside mechanism.
Since there is no knob or handle on the interior side of the door, there is nothing on which to hook the DOOR BLOK. For these types of doors, you're going to need to use a LOCK BLOK.
DOOR BLOK XL Schematic
Not Sure Which One to Order?
Take a tape measure and check the length from the inside spindle to the outside spindle. If the length is more than 10", you're going to need DOOR BLOK XL. Otherwise, save a buck and order the original DOOR BLOK.
