okay first off obvs a lot of negation over whats good, whats not with this. Everyone differs w play like this, and things can change on the daily too. thats a given w any kind of kink play tho.
Some basics on a blade to use;
the shorter the blade, the better the control over it. 2.5 to 4 inches (roughly 6 to 10 cm)
do not use serrated edges (can cause hella damage)
fixed blade knives are best, go for a full tang blade (where the body of the blade extends all the way into the handle)
for folding blades, it has to be one that locks securely so it doesnt do anything unexpected
double edge blades = hella risky. dont. way more chance to fuck up here. single edge is always best.
Some safer alternatives to knives that are also really good to determine how the bottom for this will react to similar sensations
wax removal knife (wood, plastic, whatever)
blade thats been blunted / isnt sharp (sidenote; be sure its done properly bc if its improper, it can make it more risky!)
heck even a fork isnt a bad idea
KNOW WHERE IS SAFE TO CUT IF THATS THE SORTA PLAY YOURE DOING some areas are MUCH higher risk than others due to major veins/arteries being closer to the surface.
if theres any chance of breaking the skin, even lightly, sterilize the blade before hand. medical sterilizers sprays or medical alcohol swabs are good options.
if you can, sterilize the area for play too. best practice tbh.
ALWAYS have a first aid kit on hand and make sure its stocked!! be sure you also know how to administer first aid for the kinds of wounds this can cause. accidents can always happen.
if youre cutting clothes off or smth, make sure the sharp edge is facing AWAY from the body
dont do a bunch of other things at the same time. keep it simple.
if theres any chance you or your partner might slip, don't do knife play. make sure youre both in positions that aren't precarious!
similar note; make sure the blade, its handle, and your hand thats gripping it are NOT slippery! (with lube, body fluids, whatever)
when its not being used, put it away properly. either in its sheath or properly folded closed.
Some ideas for play
sensation play is common af here. heres some ideas;
drag the point very lightly against the skin.
gently scrape the edge as if you were spreading butter on toast.
poke with the knife tip. (boop!)
using the dull side of the blade (not the edge!) press it into their skin in a line
press the flat of the blade against bare skin so they feel cold metal - for a bit extra on that, put the knife in the fridge or freezer beforehand.
Dont let it get too cold bc frozen item + skin = now its frozen to ya.
mindfuck time! make sure they see the knife, but then blindfold em. use a fake knife then. makes it safer but theyre not gonna know :3
during threats, pair it with words, and hold the edge towards them. when you actually put the blade close to them, use the dull side.
cut clothing off by slipping the blade underneath and bringing the edge up away from the body
Note: try the techniques on yourself first, so you know what it feels like and how hard to press. (like dragging the point across the skin, or lightly scraping)