A stretcher is a rigid frame usually comprised of wooden members, with expandable corners over which a painting canvas is stretched. A stretcher can also be called a canvas frame, a stretching frame, an auxiliary support or auxiliary chassis.

Since a stretcher is simply a frame, several methods can be used in constructing it and the differences in construction is determined by how the corners are built. Pre-fabricated stretchers sold in art stores come in segments with interlocking corners that can be fit together like puzzle pieces while custom frames tend to have wedges in the inner corners that enable the canvas to be tightened if it slackens and multiple cross braces as per the customer’s request.