Regarding installing on a tile wall inside the tub or shower enclosure: Sometimes it's hard to locate studs behind a tiled wall. However, as the instructions state, expanding bolts will do the trick. You don't just want to be safe, you want to avoid destroying expensive and attractive tile with a poorly attached bar. Starting and making the holes with the masonry bit can be challenging, but be patient. Also fill in under the flanges with silicone caulk before you tighten, to keep water out of the holes you've drilled. All of this is in the instructions, so mostly I'm reminding you that if you read them from beginning to end, you'll succeed and have a nice grab bar.
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