When you are getting your hide tanned you need to prepare your hides properly after the hide is off the carcase you need to flesh or take off all of the meat fat and membrane. This is so the salt can get thru to set the hair. After you have fleshed the meat off you need to lay the hair-side down in a bed of salt then put salt on the hide side and make sure that all of the edges get salt. Then do the whole salt process again. Then fold the hide nice and neat then send it off to your tannery. p.s. If you don't do this process and when you get your hides back and they have slip spots or holes this is probably why. Please don't take this offensively I am only trying to help your product turn out better. and make it a lot easer on your tannery.