(1) A manually or mechanically operated contrivance consisting of a system of rollers over which fabric is drawn at open width for the purpose of inspection.
(2) To inspect fabric in a vertical (hanging) position or at an angle inclined upwards away from the source of light.
Note: The inclined position on a manual perch is obtained by holding the fabric forward when required. On a mechanical perch the angle is fixed by a low front roller. The purpose of perching is to inspect the product at different stages of manufacture and processing.
Textile Resource (http://www.textile.org.uk)