Typically, you would need to block a finished needlepoint canvas before turining your needlepoint kit into a cushion, framing it or upholstering furniture with it. The process of "blocking" is done to straighten your needlepoint work so it stays in shape correctly.
Take your needlepoint and lay it flat design side up. Spray it with water until it is fairly wet. Wait ten minutes for the water to seep into the tapestry, then do the same thing on the other side. After the tapestry is quite wet but not soaking pull it into place as much as you can with your hands.
Lay it face down on the board. Apply the 90° ruler to a corner. Line up the needlepoint with the ruler and staple to hold it in shape. Continue using the ruler, pulling the needlepoint into place and stapling. Do this all around. If the tapestry starts going askew, take out the staples and start over from the point where it is no longer straight. When you finish, check all four corners with the ruler to make sure everything is correct. In order for the needlepoint to be even you shall have to staple every inch so this is a good time to fill in large spaces left unstapled. This is to avoid a wavy line as the tapestry will shrink as it dries. Then spray the tapestry so that it is really wet. You may have to spray a few times while blocking the needlepoint as this will make it easier to handle.
The next day, check to make sure the tapestry is completely dry before removing the staples.
If you are blocking a large tapestry and you can’t do it flat, use the level instead of the ruler.