Altho it took a bit of getting used to for me, the Martelli ruler helped me make the most accurate cuts. No slipping and the 'slits' keep the fabric in the same place. For the first time, my 9 patch didn't need any squaring up. Their stuff is not inexpensive but it does what it says. They just had their 50% off sale and there should be another in the spring. BTW, I'm not affiliated with them in any way. ;-)