Make sure your blade is on the correct side of the rotary cutter. When cutting, the blade should be right next to the edge of the ruler. If it is not, reload the blade onto the other side. I have a self closing Olfa cutter. My left handed friend can't use my rotary cutter because she cuts with her left hand on the left side of the ruler. The spacer, washer and tightening nut side of the cutter is next to the ruler edge. It just doesn't work right that way. Also, make sure blade is attached properly. When using a straight blade, the spacer, washer and nut are on the same side of the cutter. The blade is on the opposite side. (Personal experience). Hope this helps.