350 Series Mortise Deadlocks 350 Series Mortise Deadlock 350 Series Mortise Deadlock Yale's 350 Series Mortise Deadlock is a heavy-duty mortise deadlock that provides the ultimate security. Available in a range of functions, you can expect the highest quality and dependable security from this product. Features UL/cUL listed for use on 3 hour fire doors Non-handed and easily field reversible Easy-to-use thumbturn or double cylinder function available 2-3/4" backset Downloads Catalog Installation Instructions Close Want to learn more? Complete the form below to get the conversation started. loading YSSL10 Auxiliary Latch Special Purpose Locks D Series Cylindrical Deadbolts