Most finishers automatically block canvases before they begin the finishing process. If the canvas isn't straight, the finished product will not be attractive. The belt finisher Needle Nicely uses does not block the belt canvases. so I block them before shipping. When we moved into this location, I had a handyman put pine boards on the outside of the bathroom door so I could do the blocking there. I explained what I wanted the boards for, but he didn't understand and had to have picked the board with the most knots available. Do you know how hard it is to put pushpins through a knot? My arthritic fingers don't enjoy the process.