You can skip it in a few situations, like when tiles meet a countertop or ceiling, or when you're using tile with a factory-finished edge or mitered 45-degree corners. In every other case, trim is worth it. It covers the unglazed, unfinished side of the tile, also called the body, protects against moisture getting behind the installation, and helps prevent chipping at vulnerable raw edges, especially in high-traffic areas like floors and kitchen countertops.

Bullnose is a tile with one rounded edge built in. It installs just like a regular tile and gives a soft, classic look. Pencil liner is a thin, separate decorative strip, often used to frame or border a design rather than just finish an edge. Metal trim, like Schluter-style profiles, is a sleek, modern alternative in aluminum, stainless steel, or PVC that sits between two tile surfaces or caps an edge without matching the tile material. The right choice depends on whether you want the trim to blend in or stand out, and how thick your tile is.

Match the trim's height, or thickness, to your tile thickness plus the mortar bed underneath it, so the finished trim sits flush with the tile surface. A profile that's too short leaves the edge under-protected. One that's too tall creates a lip, which can be annoying on a backsplash and a tripping hazard on a floor. Always check this against your specific tile's spec sheet rather than assuming a standard depth.

It's doable as a DIY project if you're already comfortable tiling. The trim goes in during installation, set into the same thin-set mortar as the tile, then grouted or caulked around like normal. Where people most often get tripped up is on corners and transitions where the trim needs to be cut at an angle or meet another piece cleanly. If your project involves a lot of those areas, a professional install can help prevent rework.

Not always perfectly, and that's normal, especially with glazed or handmade tile. Trim pieces may be fired separately, and glaze can pool or run differently on a curved profile than on a flat tile. If an exact match matters to you, ask for a trim sample alongside your tile sample before ordering the full quantity.