3 Knuckle Square Barrell Hinge Specifications McKinney Three-Knuckle Square Barrell Hinge Close UL Listing UL Listing for Decorative Square Hinge The McKinney Three-Knuckle Square Barrel Hinge (SQ314) is now UL listed for hollow metal and steel covered composite fire doors rated up to 3 hours, and wood for fire doors rated up to 20 minutes. Close You may also like Square Barrel Hinge