Mark:

I use layers a lot, but as you found on the support site, all layers really do is control visibility. Objects on different layers can still interact. But if an object is on a layer that you have turned off, it won't interfere with what you are currently trying to draw - SU won't try to glue to it, etc. I put all common purlins on their own layer, so that I can turn them off and get better visibility into the model for doing other stuff. Same with floor joists. I also put dimensions on their own layer, and turn them on only for demonstrating to clients or printing. Construction lines are the opposite - I turn them off for printing and demonstrations. CB.