What Are Wedges For?
What are the little wooden Keys/Wedges for?
You should have been supplied with a bag of wooden wedges. Wedges or keys are used to retention you canvas during or after painting. This is useful if the canvas has slackened over time, during transit or after you have been applying pressure during painting.
With each canvas or frame you should have 8 wedges and 2 wedges for every cross bar.
They are very simple to use. Just put two wedges in each corner of the frame, and one at every point the cross brace meets the frame. Tap them in gently to start, making sure you work your way around the frame evenly so that you get an equal tension.
You canvas will become tighter on the frame as the joints expand!