A stretcher bar assembly is used to stretch a canvas picture around before it is framed to prevent is sagging in the frame. Typically the canvas is wrapped around the stretcher bars and stapled around the back or side edge. The canvas does need to be pulled tight and the use of proper canvas stretching pliers is recommended.
The stretcher bar assembly will be manufactured to within a millimetre of the sizes entered so it important you calculate the size correctly and allow enough wrap around dependent on how you want the finished item to look.
Typically there are two ways a canvas is stretched:
Standard Wrap - Canvas is stretched with the intention of framing it afterwards. The canvas is stretched so the maximum amount of the printed/painted area is displayed across the front. The edges of the canvas are usually unpainted or unprinted, and the canvas is stapled along the side edges. We would recommend ordering the stretcher bars approx 10mm smaller than the printed/painted area of your canvas to allow for a small amount of bleed around the edges.
Gallery Wrap - Canvas is stretched so the printed/painted area is wrapped around the sides of the stretcher bars and the canvas is stapled around the back edge. This is a popular and economical way to stretch modern artwork and photographic work as the Gallery Wrapped canvas is hung on the wall without the addition of an external frame. It is important to subtract 2 X the depth of the selected stretcher bar plus approx 10mm from the size of the printed/painted canvas you are framing to allow for the canvas image to cover the sides of the stretcher bar assembly and a small amount of bleed.