McKinney SQ3331 4-1/2 x 4-1/2 Standard Weight Square Barrel Full Mortise Hinge

The McKinney SQ3331 is a 4-1/2 inch x 4-1/2 inch full mortise, standard weight butt hinge featuring a distinctive square barrel (square knuckle) design. Unlike conventional round-knuckle hinges, the SQ3331 delivers a crisp, angular silhouette that complements contemporary and institutional architectural millwork. As a full mortise hinge, both leaves seat flush into routed mortises on the door edge and frame, producing a clean, professional installation with no surface-mounted hardware visible when the door is closed. The SQ3331 is part of McKinney's square-barrel hinge program — a go-to specification for architects and hardware consultants who require a squared architectural appearance on commercial and institutional door openings.

Institutional Grade Features & Benefits

• Square Barrel Knuckle: The hallmark of the SQ3331 is its squared knuckle barrel profile, providing a refined, geometric aesthetic that pairs naturally with modern hollow metal frames, wood doors, and contemporary aluminum storefronts.
• Full Mortise Installation: Both hinge leaves are fully recessed (mortised) into the door edge and door frame, ensuring a flush, tamper-resistant fit and a clean architectural finish.
• Standard Weight Construction: At 0.134 in. steel leaf thickness, the SQ3331 delivers dependable performance suitable for standard commercial door applications without the added bulk of heavy-weight hinges.
• 4-1/2 x 4-1/2 Inch Leaf Dimensions: This generous leaf size provides broad bearing surface and stable swing support, appropriate for standard-height commercial doors.
• McKinney Quality: McKinney is a long-established, widely specified commercial door hardware brand trusted by architects, general contractors, and institutional facility managers across North America.

Technical Details