What car? I think you're asking about the rear caliper bolt on a MKIV? If so, some wrenches fit, some don't. Take what you have, go under the car, and see if you can get it on the bolt. Done.
I am getting prepared for the rotor and brake job in a few days and want to be ready for anything as I won't have another vehicle to go to the store if I am missing the right tool. I have been reading about the 15mm wrench issue on the forums here. Some have said you absolutely need the thin wrench while others say they used a standard and it worked fine. Well, I measured out my Craftsman wrench and found it to be 1/4 inch in thickness. I happened to have a cheap chinese version of the 15mm wrench and found it to be thinner. A good 1/16" thinner in fact, which is 1.6 mm less thickness. I am thinking this should do the trick. Any thoughts? I am heading out to the get the remaining parts I need in a couple days so if I REALLY need that thin 15mm wrench, I better pick one up.
I've been able to do several rear brake jobs using a standard craftsman 15mm. At least for me, I can't get the wrench completely on the guide pin, but I can get it about half way on and that's enough to snug up the caliper mounting bolts.
That said, I've made a note to pick up a slim 15mm for the future as it would make the job a little bit easier.
As a follow up to this thread, I just want to report that the thinner chinese 15mm wrench fit in there perfectly. The 1/16 inch difference was all you needed. I had found this one in a cheap home repair kit that someone had bought for me a while ago. I tried a couple other things to see if I could jury rig a way to hold that nut in place but nothing was strong enough because the bolts were on there pretty tight. Someone else reported that the standard 15mm would work. I could not verify because my Craftsman set only went up to 14mm. My earlier size measurement was based on that 14mm and I would have to assume the 15mm was at least as thick. The 14mm was too thick when I tried it.
Bottom line: If you are doing this job, you had better get the bicycle wrenches as suggested in an earlier response or do a comparison on ALL the 15mm wrenches that you have because you might just find one to be slightly thinner and that will do the trick.
Bench grinder is your friend!...I took an old open end wrench and went at it with a bench grinder to reduce jaw thickness...works great..done several VW brake jobs with it!
96 Golf...Gone...But not forgotten..Great ride!
2000 Passat GLX...Gone...But not forgotten either..have scars on my knuckles from all the "wrenching" to keep it on the road!
2008 Rabbit S, VWsport springs/OEM shocks, GTI brakes all around, GTI rear swaybar...best balanced car I've had in a while!