Wall Entity

[Kreekakon]

In that case, aside from what Traggey said, you can place down a random entity, select it and click on "..." on the right to replace it with your own.

I wouldn't recommend this method over Traggey's though. Even though it's faster in some situations, if you close the map, and reopen it later to edit it some more, the map editor still won't be able to find the enitity if it's not in "resource range"