I don't cut thru more than 4 layers. Some people put little sandpaper dots on the wrong side of the ruler that goes against the fabric. I just try to keep an even pressure and put my little finger of my left hand (I'm right handed) on the table braced up against the edge of the ruler to keep it from slipping. When I start having issues, it usually means I need to change my rotary cutter blade. I'm bad to forget to change them.