These guards look like they just snap onto the door edge. Is there any adhesive needed or do they hold themselves on by pressure?

 

I wouldn't use them unless you are worried about the cars next to you. Cause they don't protect from people opening their doors into youre car. The ones ive seen have had no adhesive and they can scratch door edge paint over time.

 

As stated above they serve no useful purpose other than scratching your paint when trying to install them and as stated they don't stop other people from opening their door on your car.

 

OK. So what do you think about the wheel well guards? I've heard they can hold water and cause rust???

 

They are needed for the wheel wells. I installed my door trim to keep to original.

 

Am installing a luggage rack also. What would be a good thing to put on the screw threads or in the holes to keep the drilled holes from rusting?

 

I have door guards on my 94 and hate them... I can never remove them because they've scarred the paint beneath them to no return.

They haven't provided use to me at all.

 

First, use stainless fasteners. There are any number of fastener caps that cover the screw. Use chrome ones. There are several different products out there you can coat the hole with that will stop any corrosion. Use one of those that dries on like heavy wax.