General Definition
A tile anchor is simply any anchor or toggle bolt specifically designated for drilling into wall tiles. When you purchase a wall-mounted fixture, such as a towel bar for your bathroom, it sometimes includes tapered anchors or screws that simply do not hold well on tile surfaces, especially if the tiles to be drilled are not directly over a wall stud. When this happens, you can run down to your local hardware store or home improvement store and invest in a set of wall anchors specifically labeled for use on tiles. Typically these anchors will be tube-shaped rather than tapered.
Specific Use
To install tile anchors, you must first drill the appropriate holes into the tile. If you must drill multiple holes, carefully measure the space between the anchors to ensure you drill in the correct spots. Use a drill bit specified for tile and glass in the size specified on the anchors' packaging, and insert the anchors into the holes. From there, you can mount objects against the anchors and fasten them by inserting the appropriately-sized screws into the anchors.
Why Tile Anchors?
Not all anchors are created equal. Wall anchors (like those designated for tiles) are designed to absorb shock, keep out moisture and protect from corrosion. Their size and shape enable them to hold firmly for years without tearing or chipping the drywall or tile. Tile anchors are ideal for supporting fixtures such as shower rods, towel racks and toilet paper holders.
Caveats
Before drilling into any tiles in your home, check any existing warranties. Drilling holes into the tile may void your warranty, and natural stone tiles are especially prone to cracking and etching if not managed carefully. Natural stone tiles would include marble, granite and limestone. Only use glass-and-tile drill bits when drilling into tile, and when purchasing wall anchors, read the packaging carefully to verify that the anchors are indeed designated for tile surfaces.