When you see red on the bottom, the contraption mode is enabled, the red box is a warning that all your props will be unfrozen when you grab them.

My prop movement system for DarkRP. Uses the Debris Trigger collision group on your entire contraption when you use physgun, and keeps track of what props you grab, to set everything right when you let go. Also no collides everything together. Can be enabled and disabled with ALT+R.

This is revolutionary in gmod movement as you can move hundreds of welded props at once without an issue!