A relegendable key is a key whose legend can be changed non-destructively. It consists often of two parts, one bottom and an removable top. Most relegendable key variants are flat. Relegendable keys are most often found on programmable keyboards, such as point-of-sale keyboards where ease of customization to the store's inventory is important.
Some key tops are transparent allowing for a piece of paper to be put in-between. Some vendors, such as Tipro offer also opaque printed key tops. Some keyboards (like the Cherry G80-2100) have relegendable function keys with a default legend printed on the bottom, visible through the clear top.
Most relegendable keys that are larger than one key span attach to two (or more) key switches -- not a single switch and stabilizers.
Cherry MX compatible
Used on Genovation's programmable key pads. High profile, but different in shape from top row keys.
Signature Plastics DCS
Top row of Signature Plastics' DCS family, the clear lid exposes both the top and front of the key.
Lowest profile. There are two versions that are incompatible with one-another. See Tipro
Not Cherry MX-compatible