Automask is a very easy feature to use when you are compiling your tileset.
To put it simply, this feature allows the player to walk through / past anything that was transparent in your image. Anything that's NOT transparent in your tileset will be "masked" which means players, enemies, etc . . . can walk or rest on it.
TO USE AUTOMASK:
When you start making your tileset, automask is automatically turned on until you change it. If you changed it, you can still turn it back on by choosing it from the top of the menu.
You must remember that for better tilesets you must make your own mask file. This is because stuff like poles, vines and spikes have to be masked in a certain way. You should also keep in mind that any edges that are too rough will cause the player to get stuck in the scenery - meaning they'd have to JJK themselves.
Added on: Saturday, June 2 7.31 am. Made by Ice M A N.