When cutting the rug canvas to your desired size add at least 4 squares onto each side.
A brand new piece of rug canvas will have a thick edge at both the top & bottom which needs to be cut off since you cannot hook through it. The canvas thread from these cut off edges is very strong and is useful in tying down the edges and being used as a needle threader. So pull off a few pieces of this canvas thread.
Count at least 4 squares on each side to fold down and use the canvas thread to tie the edge down. I made ties at every blue line on my canvas or about 10 squares. Most videos or instructions I saw online did not have this step but I found the large canvas easier to handle with the edges secured.
The corners get a little difficult since there are now four layers of the canvas folded there. Do not try to cut parts of it away to make it easier to loop through. Trust me, I tried and it didn't work. Use the wide end of the locker needle to align the holes for tying.
Here is a short video showing how I tied the edges and corners: