The Schlage L583-585 is the OEM set screw for the SL1 Lever and SK1 Knob ligature-resistant trim assemblies in the Schlage L Series mortise lock family. Specify SK1 Knob or SL1 Lever at time of order. This is a single screw, not a pack. It is the concealed fastener that secures the SL1 or SK1 trim body to the lock chassis - a component that is deliberately hidden as part of the anti-ligature design of these trim types.

This is not the same set screw used in standard L Series lever or knob trim. Standard rose and escutcheon trim on the L Series uses set screws that are accessible from the outside. The SL1/SK1 trim uses concealed fastening hardware specifically to prevent access to any grip point or anchor that could be exploited in a ligature attempt.

What the SL1 Lever and SK1 Knob Are

The Schlage SL1 (Solid Lever, Style 1) and SK1 (Solid Knob, Style 1) are the ligature-resistant trim options for the L Series mortise lock chassis. They are documented in the Schlage L Series Service Manual and carry the Allegion "Paperclip Protection" designation from NYS-OMH (New York State Office of Mental Health) testing, enabling their use in low-, medium-, and high-risk behavioral health environments.

Both trims use a smooth, tapered profile with recessed surfaces and no horizontal projections. The lever on the SL1 has no ledge, lip, or wing that could anchor a cord or flexible material. The knob on the SK1 is a rounded, tapered profile without any graspable edges. The trim dimensions are tightly controlled: the SL1 measures 3-7/32" x 6-1/8" x 3-1/8" and the SK1 measures 3-3/16" x 3-3/16" x 2-5/16". Both are engineered to meet IBC and NFPA requirements for healthcare occupancies.

The SL1/SK1 trim is available in 22 mechanical functions and 9 electrified functions, making it the standard specification for behavioral health facilities, psychiatric inpatient units, correctional facilities, and detention centers where standard lever or knob trim is not acceptable.

Schlage Set Screw: Why Concealed Fastening Matters on Ligature-Resistant Trim

Standard L Series trim uses set screws that are accessible with an Allen key from a position visible on the trim body. On the SL1 and SK1 ligature-resistant trim, the fastening hardware - including the L583-585 set screw - is installed in a concealed position that is not visible or accessible from the corridor side of the door without authorized access.

This concealment is not just about aesthetics. An exposed set screw head on a trim assembly is a potential ligature anchor point. A cord wrapped around the protruding hex socket of a visible set screw could create an attachment point even if the lever itself is ligature resistant. The L583-585 set screw is positioned and recessed in a way that eliminates this risk, which is why the Allegion SL1/SK1 description specifically calls out "concealed fastening hardware" as one of the design features that qualifies these trims for behavioral health applications.

Schlage L Series Mortise Lock Parts: L583-585 vs Other L Series Set Screws

The L Series set screw catalog includes several different part numbers for different trim types and applications. The L583-585 is specifically for SK1 knob and SL1 lever trim. The L583-902 is the set screw used in standard LV (lever) lock case assemblies - a different part for a different application. The L283-615 is a pack of three L583-902 screws plus an Allen key for standard lever lock case replacement.

Do not substitute other L Series set screws for the L583-585. The geometry, thread size, and positioning requirements for the SL1/SK1 concealed fastener are specific to that trim assembly.

For the complete Schlage L Series trim, hardware, and mortise lock parts catalog, SecurityParts stocks OEM components.