I tried the "no bringing parts" way. It was short lived. I'm not profitable enough yet to transition. I think the bay rental fee for holding up my lift with incorrect parts is great idea. Or maybe letting them know that if there is a delay with parts, there will be a delay in finishing their car because you will need to move on to the next car. But honestly, it's not that big of a deal most the time. I don't give any warranty when customer supplies any portion of parts. No warranty for correct installation either. Nothing, zilch! It's written on my work orders and I tell them. I don't mind if they get cheap parts as long as they are correct. If the part fails then they pay me twice! But we all know that their aftermarket parts can fall just like the non dealer parts we buy. I offer diagnosis but don't haggle when they insist that auto zone already gave them 1. I don't try to make them feel stupid for listening to auto zone. I simply say "hey, we can start there if you like and see what we have after." Therefore, I get the initial repair and the correct repair afterwards. Same thing with their wrong or crappy new part. Some customers bring their own parts because they haven't been educated on what's different about letting a shop get them versus not. I educate the pace of mind factor so they can weigh their savings now against there potential loss in the possibly near future. Also when they get their own parts I make them get everything like brake cleaner, grease, shop towels, cotter pin, top off fluids, etc. Abd I let them no if I need something else I'll call them. I don't pick up items from the part stores for them. Nor call the part stores on their behalf, nor give cores back before I'm completely satisfied with job. So they must pay their core charges. It only takes a time or 2 that I have to call a person to say a seal is missing or incorrect and "i need you to come from across town to bring me that asap, or I can pick it up for you at a higher markup than I normally would have charged". I do it all with a smile and they usually do return because they like my work and charm, but let me get parts next time to avoid hassle.