Item list. Setting the high nibble of the first byte to F will cause the item to be nonfunctional and you can walk through it. Once placed, it cannot be removed!
Example: A normal pinball machine is 0701. A nonfunctional one would be F701.
Edit: Why wasn't Vash's item list from this topic posted here? It's missing now, but it would have saved me time if it was here.
Edit 2: The high nibble also seems to be used for something with insects/fish; most likely size.