Measuring fence clearance?

What's the simplest method to put a fence or wall into a RDK model, and measure the distance from that fence to the closest part of the robot at different robot poses? I don't need high accuracy, just a decent idea (within 25mm or so). I'm trying to determine if I'm going to have to relocate some fences to achieve safe clearance.

Is there a way to get a measurement like this, or would I need to set up Collision Checking? Since I've never done that, does anyone know of a good Idiot's Guide to collision-checking in RDK?

So, it looks like I would have to import a model of the fence as a 3D object, then activate the collision checking between the robot and the fence?

Hm... should be doable. My big concern is actually my "safety tool" sphere surrounding the actual physical tool, so I'll need to model that and attach it to the robot. And it probably has its own entry in the collision table, I'm guessing?

This whole mess is b/c I need to retrofit dimensional safety (virtual fence, virtual tools, etc) into a production system that was set up without them years ago, by people who didn't know what they were doing. So the tool-change stands are located very close to the physical fence, and I have to do all my prep work 100% offline, b/c when it comes time to go on-site, we'll only get a few days of downtime to make all the changes before this system has to go back into production.

So, I have the tool dimensions, I have the customer's tape-measure distance from the robot base to the fence, and I have a copy of the tool-change program. And RDK. Well, time to get to work....