I use a rubber coated wire, but have used plain old yarn in veg...you just don't want anything with fuzz once the plant is flowering, because flowering plants are sticky...and everything sticks to them...and then you end up with little fuzzies in your pot...which doesn't really matter all that much...but if you make hash with your trimmings the hairs get on my nerves because you see them later in the hash you are left with...so I started using rubber coated wire...