Use the other end of the piece of wood?
That assumes that the 2 ends are different and that you don't need the entire piece of wood except the piece you were originally sawing off. If you need 4' piece of wood and if its too short you can't attach it but if it's too big it won't fit and your current piece is 5' then you need to cut 12" off it. If you cut 13" you made it fit but now you can't attach it because it is too short. Flipping the piece of wood around is not going to help your case because the length hasn't changed.