A permanent map, also called a perm map, protect map, or locked map, is a map that cannot be removed. Therefore, you cannot vote for them.
Unlike official maps, permanent maps occur with the same rarity as regular user made maps.
If you own a permanent Map and open it in the Map Editor, you aren‘t allowed to change it and there is a banner which reads "This map is now permanent. You cannot change it."
In-game, you can recognize a permanent map by looking at the creator's name in the top left corner of the map. If the map is permanent, there will be a lock icon next to the name.
A map can be made permanent by taking part in the Map Making Contest.