Hinge — function, parts, types, uses, and history

Parts and characteristics

Typical hinge components include two leaves (plates) that attach to each object, a knuckle or barrel where the leaves interleave, and a pin that runs through the barrel to form the pivot. Materials commonly used are steel, stainless steel, brass, bronze and engineered plastics; finishes and coatings protect against corrosion. Some hinges include ball bearings to reduce friction, springs for self-closing action, or friction elements to hold a position. A "living hinge" is a single flexible piece of material, often molded plastic, that performs a hinge function without separate hardware.

Common types

• Butt hinge: standard residential hinge mortised into door and frame.
• Piano or continuous hinge: a long hinge running the full length of a lid or door.
• Concealed hinge: used in cabinetry for a hidden joint.
• Strap and decorative hinges: for gates and visible furniture fittings.
• Pivot and pintle hinges: carry loads at a single point and allow different swing geometries.
• Friction and spring hinges: provide resistance or automatic movement.

History and engineering applications

Hinges have a long history: simple hinge-like fittings appear in archaeological finds from antiquity, where metal and wooden pins allowed lids and doors to move. Over centuries, hinge design evolved to meet architectural, naval and industrial needs. In modern engineering, hinge principles are used in everything from cabinet hardware and vehicle doors to swing bridges and rotating machinery. In specialized civil engineering, pivot bearings or hinge-like joints are incorporated into structures and foundations to accommodate movement and reduce stresses when ground conditions or thermal expansion would otherwise cause cracking or failure; very large articulated joints are sometimes specified for those purposes.

Installation, care and safety

Hinges can be surface-mounted or mortised into the attached members; correct screw type and placement ensure load distribution. Regular maintenance—cleaning, lubrication of pins or bearings, and checking for loose fasteners—extends service life. Selection should consider load, cycle frequency, environment (corrosion, temperature), and required swing range. For doors and openings in public buildings, fire-rated and self-closing hinges may be required. Small decorative hinges are used in boxes and fine furniture, while heavy-duty pivots serve gates and industrial equipment; examples of fine fittings include jewelry box hinges often made of brass or plated metals (small hinges), and large engineered pivots used in heavy structures and foundations (large hinge applications).

Different hinge arrangements determine how an attached object moves: direction of swing (inward or outward), clearance needs, and whether the hinge is reversible or handed. For information about door hardware layouts and common frame attachments see resources on standard door installations (door frames and fittings).