In multi-material applications like millwork, tile, stone, or glass, material depth refers to the thickness of the finished wall surface the device passes through. Measuring this thickness is the first step in selecting the correct device depth (short, medium, or long), typically by aligning it with the closest standard reference-approximately 1/4" (6.35 mm), 3/4" (19 mm), or 1-1/4" (31.75 mm).