These painting canvases are made from 1-1/2" by 3/4" or 2-1/2" by 3/4" select pine lumber. I used pocket holes to fasten the corners and then reinforced the corners with metal L-brackets for canvases smaller than 36" and with 1/4" or 1/2" plywood triangles to reinforce corners on frames larger than 36". Once the frames are made, canvas can be stretched over them and fastened with staples on the back side.