nedarim 61

summer is the time of ripe fruit and sharp knives.

if vow not to benefit from something until the end of summer. debate about what that means and when does summer end. one suggestion is when the fruit picking is over and the knives are put away.

shabbat 123

professional knives need to stay sharp and so shouldn't be used on shabbat.

so, don't touch or even move the shoemaker's knife, the butcher's knives, the carpenter's drawknife; or paper-cutter's knife.

(this week, I couldn't find the scalpel I use for paper-cutting, so had to buy another one. so if you earn your living from your tools, best not to use them for just anything, as might lose them as well as damage them...)