Arrow E50-26D-234 Satin Chrome US26D Grade 2 E Series Occupancy Indicator Deadbolt, specially designed with a large external viewing window that signals when the room is occupied. This occupancy deadbolt uses an emergency key override to unlock the door from the outside in case of emergency. When the deadbolt is in a locked position , an external slot is exposed that provides for the use of the override key. When the key is used the key is captured in the deadbolt and cannot be removed until the deadbolt is retracted or turned to the "in use" or unlocked position. Ideal for restroom facilities, and other areas requiring visual notification of use and security privacy. This deadbolt has two piece housing, with free spinning outer ring to prevent wrenching. This lock is ANSI A156.5, Auxiliary Locks, Grade 2 certified. The thru-bolting is supplied with two 1/4" steel thru-bolts. There is a 1" solid steel deadbolt throw with hardened steel pin insert. For doors 1-3/8" to 1-3/4" inches thick. The Strike is supplied standard with #346 security strike for metal frame. the deadbolt front is 2-1/4" x 1-1/8" standard for 2-3/4" backset. All functions a reversable, for right or left hand applications.