After having a scalpel seam ripper come out of its sheath and stab me right through my notions bag I found a neat carry case that was the notion of the month at our fabric store quilters club. I too find it safer and easier with a good handle on the ruler, my preference is the new ruler gypsy stlye as they stay on the ruler better and it slips less. That rotary cutter must have slipped big time to hit your knee as most of us dont cut on our laps! Hope it healed well