National Marker N350777 Square Spring Door Hinge 3.5 in

Product Description

The NATIONAL MARKER N350777 is a 3.5-inch square spring door hinge finished in satin nickel, designed for self-closing door applications in residential, commercial, industrial, and institutional settings. Part of the V520 series, this hinge features adjustable closing tension and adjustable closing speed, giving installers direct control over door return behavior. It is listed for fire-rated openings, making it a code-compliant choice where self-closing hardware is required. Constructed from cold-rolled steel, the N350777 is built for durability in high-cycle environments. Square corners fit standard hinge cutouts without modification.

This hinge is suited for a wide range of door installations where self-closing function is required by code or building specification. It performs in residential entry and interior doors as well as commercial and institutional corridors, stairwells, and rated assemblies. The adjustable tension and speed settings make it practical for doors of varying weight and swing frequency. Licensed contractors and finish carpenters typically specify this type of hardware when a fire-rated self-closing assembly is required by the authority having jurisdiction.

Key Features

• Adjustable closing tension allows field calibration to door weight and use frequency
• Adjustable closing speed for controlled door return without slamming
• Listed for fire-rated door openings — supports code-compliant self-closing assemblies
• Cold-rolled steel construction for strength and wear resistance
• Square corners fit standard hinge cutouts with no mortise modification
• Satin nickel finish suitable for residential and commercial aesthetic requirements

Compatibility

Designed as an OEM-style replacement and new-installation spring hinge for standard 3.5-inch hinge cutouts on residential and commercial doors requiring self-closing hardware.

Installation Notes

Installation is typically performed by a licensed finish carpenter, door hardware installer, or general contractor. Before installing or adjusting tension, ensure the door is secured and will not swing freely during work. Use the manufacturer tension adjustment tool or a flat-blade screwdriver as directed to set closing force after mounting. On fire-rated assemblies, verify that all components of the door opening meet the listing requirements of the applicable fire door assembly standard before placing the door in service.

Technical Specifications

• Series: V520
• Hinge Size: 3.5 inches
• Corner Style: Square
• Finish: Satin Nickel
• Material: Cold-Rolled Steel
• Fire Rated Listing: Yes
• Weight: 0.779 pounds
• Sold As: Each

Standard Information

• Brand: NATIONAL MARKER
• Manufacturer Part Number: N350777