are you talking about grow cubes like grodan? if so they should have a hole in the top already, just ph the water you will be soaking them in, soak the cubes for at least 30 min, the place your sprout in the cubes, if your using jiffy cubes, or rapid rooters, then just use a no.2 pencil to pok a hole about 1/4" deep and place the sprout in the hole. be careful not o break or harm your new seedling