pleat

A pleat is a fold pressed or stitched into fabric, typically running the length of a garment panel. Unlike random creasing, pleats are engineered folds that serve two primary functions: they allow controlled fullness for movement (particularly in skirts and trousers at the hips and thighs), and they can absorb excess fabric while maintaining a clean silhouette. The fold is usually held in place by stitching along part or all of its length, and sometimes set permanently through heat and chemical treatment during finishing.

The main pleat types differ in how the fold is oriented and stitched. A knife pleat is a single fold pressed in one direction, typically with both layers stitched down flat, creating a sharp crease. An inverted pleat reverses this, with the fold opening toward the garment exterior. Box pleats consist of two folds facing away from each other, leaving a central ridge. Accordion pleats are multiple narrow, parallel folds, often set permanently in polyester or synthetic blends. Kickpleats are small slits with internal pleats at hem edges, common in pencil skirts to permit stride.

Setting and stability

Most pleats must be set during finishing to hold their shape through wear and washing. This typically involves pressing under steam and pressure, sometimes followed by a resin or chemical treatment (particularly on natural fibers like cotton and linen) to lock the fold permanently. Synthetic fabrics like polyester can be heat-set more reliably. Poor setting leads to pleats opening or shifting during wear. Washability varies; some permanent-set pleats survive repeated laundering, while others soften or collapse if washing temperature, detergent, or agitation is too harsh.

Pleating adds significant labor cost and requires precise pattern marking and stitching. The fabric must be cut generously to accommodate the depth and length of each fold before pressing. A typical knife pleat might consume 2 to 3 inches of flat fabric width. Designers balance the number and depth of pleats against manufacturing time and final garment weight, since deep or numerous pleats increase bulk at seams and hems.

The term originates from Old French pleit, meaning a fold or bend. In the trade, pleats are specified by type, depth (measured in inches or centimeters), and length (how far down the garment the stitch line runs). Partial pleats, stitched only from the waistband to mid-thigh, are common in skirts to preserve the pleat's movement benefit while reducing weight and seam strain at the hem.