Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: Would this work on a RV shower door that is 1/2"
Document: I used large self-adhesive photo bumpers and they work great. Other suggestions I have read are to use sponge make-up applicators to place between the door and the frame interior. The clearance between front to back for hanging over the shower frame is 2-1/8", plenty of room for almost any door. I had searched everywhere for an item like this one and there are no others to be found. This is just what I needed.
This product said it would fit "over any door"...well, I have standard interior doors and this rack hung way over the front and the clips over the top would not allow the door to close...also, the description needs to be specific about what type of shower door it will fit over; I knew it would not work on my frameless glass door, but the description did not say this.
I had to return this item, It did not work for me. I sticks out far from the back of the do I could not open hte door completely. My bathroom is to small for that to happen, Also, I should have paid attention to the other reviews. The rungs are really close together. This I feel would work best if it hung on a shower door and only hand wash cloths and hand towels on it. It is much to small for full size bath towels.
This towel rack works just as promised. It fits nicely over the shower door and is a perfect size for a wash cloth...which is just what I wanted it for. There are also 2 hooks that are great for hanging small brushes like nail or back scrubbers. I have only had this rack for about 3 weeks now, so I am curious to see if it ever starts to rust...which would then downgrade my rating from 4 stars.
3 major flaws.... 2 of which made assembly impossible, one we could correct ourselves (though we shouldn't have to) and the other, we could not.1)  One of the ceramic ends did not have the hole bored out large enough for the screw to go through... we corrected that, though without the right tools, we couldn't have.2)  One of the ends of one of the rods was not threaded to take any of the screws provide, nor any we had.
I can't figure out for the life of me why they would make this item with such large top part that fits exterior doors. I couldn't use this in my bathroom because I have standard doors (1 3/8"), which means that these were too big in width at the top and kept wobbling and being very noisy, not to mention scraping the door at the bottom since the side rods weren't vertical, but at an angle towards the door.
But, the picture doesn't show that the top holders are 2 inches or so wide. It did not fit over the thin shower door.... My sweet boyfriend tweaked it and also added padding so the unit wouldn't bang against the glass.
The brackets are too wide for a shower door, but works okay on a regular door. I had hoped to hang 2 towels on it, but it really only works to hang one bath towel, and a washcloth and/or hand towel.
I have been shopping for a while for a over the door towel rack, and have returned several.This is a quality item, with no assembly required. You can hang it over the shower door OR you can hang it over the bathroom door.As mentioned in over reviews, the width of the brackets that go over the door is probably more than anyone needs, but there are several simple work-arounds that can fix this problem if you encounter it.
This towel bar has a great design and fits our needs just right. We are using it over the shower door and are able to place 2 bath towel plus smaller ones for use. We have a small bath room and its compact design is great. Plus it has a nice design
Answer: The U shape that goes over the door is 2 1/4".  Our doors are not that large either. I took a strip of felt that you use on furniture for hardwood floors and lined the inside of the U shape.It created a shim and works just fine. Hope this helps.