Player able to pickup items behind impassable wall

[stevet1]

I've got some small spaces containing items that the player should have to open to get the item, but despite the items showing as behind the wall (in ultimate doom builder - which I believe represents the item as it's in-game size) the player can pick them up if they run into the wall. How can I stop this? I don't want to move them back as that would look odd. I have a workaround of using custom items with smaller sizes, but is there an easier way I am missing?
Thanks.

[Logan MTM]

So many ways to do that!

1 - Change the Actor Radius property in Decorate/zscript

2 - Change the Actor SOLID flag with ACS...

3 - Change the Actor State to whatever else A_SetSolid/A_UnSetSolid... (Decorate + ACS)