The majority of piano makers install the case, also known as the outer rim, to the frame or rim once the pinblock is in place or after assembling the pinblock, soundboard, bridges, and strings. In some pianos with continuous rims, like Steinway grands, the case and rim are constructed together.

In grands, the case's removable components include the large lid and the front lid, which are hinged to each other, the fallboard, and the key slip. In vertical pianos, various panels enclose the front of the piano, along with the fallboard and the key slip. The top lid of vertical pianos is typically opened by swinging it front to back, although some verticals have it hinged on the left side. The key bed in verticals is easily removable when it is only screwed and not glued to the case's sides.

Piano panels can be constructed from solid wood, plywood, or particleboard. Solid wood panels are usually veneered on both sides to prevent warping. Particleboard is heavier than other types of panels because it contains a lot of glue, and a grand lid that seems heavier than usual may be made of particleboard. One significant disadvantage of particleboard, apart from its weight, is that screw holes in it are easily stripped. Therefore, a particleboard panel may be fitted with solid hardwood inserts wherever hardware is attached to it with screws.