You are supposed to place them on a tree stump so that the salt dissolves and runs down the tree then the deer lick the tree to get the salt. I fell a fir next to or on a regular deer path at chest height then run the tip of the saw down the stump about twelve inches then place the salt block on top depending on weather they can last upto six months and I think they do work maybe because we have very poor soils here but when the deer get over their weariness they seem to use them fairly regularly.