The Townsteel CRX-K-84-32D Ligature Resistant Cylindrical Knob Lockset In a Classroom Function With a Schlage "C" Keyway Standard, Keyed Random 2 3/4" backset, In a Satin Stainless Steel Finish. The CRX-K-84 Classroom Lock Is Ideal For Use in Behavioral Health Care Units, Institutions. CRXK Series cylindrical lock is ANSI/BHAM Certified grade 1 with ligature resistant knob trim. It fits standard 161 door prep.