Due to moisture and use, the material of the stretcher frame can slacken. With the help of wooden wedges, you can counteract this and re-tension the frame..
1. Before starting
Insert the wooden wedges into the miters from the corners, two at a time. IMPORTANT: Do not drive them out yet.
2. After drying
To tighten the fabric, carefully drive each wedge in. The frame will be larger and since through the fabric tighter.
Note: Only if necessary! The material should be completely dry!