Having had problems with puckering when ripping, I carefully cut off the selvedge with scissors; fold the length of the fabric in half twice (only) so the cut edges line up (to reduce cutting slippage from having too many layers) and folded piece fits on cutting board. Measure width of strip and cut a short cut at each folded edge of fabric, then turn too-narrow ruler back to line up with these slits and cut the rest of the way.