I have a terrible time keeping my ruler from slipping. I've read the tip on sandpaper but was just too lazy (or scared) to tackle his stuff to find sandpaper! Today though after ruining 3 blocks from slippage I braved it. Its probably heavier sandpaper than I need but oh wow the difference! I glued a few small pieces to the back of my ruler and it stays in place! Now to go out (once the rain stops) and buy me some sandpaper...preferably some sticky kind so I don't have to wait on glue to dry!