I just buy a mineral block at TSC for a few bucks and put it on the ground. The rain will dissolve it. I usually end up putting out about three each Summer in each lick. Over time, the deer will continue to visit the lick. I started a new lick this June, and the deer are still hitting it pretty hard. Of course the action will slow down as Summer comes to an end. It's just a way to help the deer with nutrients during a time when they need them.