inlay, set, mount
鏤 centers on embedding decorative material into a surface: inlaying, setting, or mounting something into a base object.
鏤 combines 金 (metal) with 婁, which likely contributes the sound and may relate to the idea of piercing or attaching, fitting the inlay sense.
Metal 金 is used to inlay or set decorative pieces into a surface, with the right side 婁 suggesting the intricate work of mounting.
For ル, imagine a jeweler inlaying a tiny ruby: ruby -> ル, and the metal setting holds it in place.