Hair stackers are a useful tool. Used get the ends of the likes of deer hair nice and even to give your flies that classy look.
Ideal for tails and the like.
Straight hairs stack best, cut out a clump about the size you need, remove any under fur/fibers either by gently pulling them with your fingers or using hair combs
Pop the hair in pointy bits down and tap your stacker several times on a hard surface