MDF
Standard MDF is flat, consistent and economical. It routes cleanly and accepts paint well when correctly sealed. It is a strong choice for indoor prototypes, templates, display parts and painted components. Edges are more absorbent than faces and need preparation for a high-quality finish.
Moisture-resistant MDF
MR MDF is formulated for improved resistance in humid conditions, but it is not waterproof. It still needs suitable sealing, finishing and detailing. The familiar green colour is an identifier, not a guarantee that any finished product is suitable for wet or external use.
Plywood
Plywood offers layered strength and a visible edge. Its appearance and machining behaviour vary with species, grade and manufacture. Voids, patches, face variation, warp and local thickness variation can occur. A requirement such as “clean visible face” needs an agreed material grade and inspection standard.
Nominal thickness and fit
A sheet sold as 18 mm may not measure exactly 18.00 mm. A slot intended to grip the sheet, a flush pocket or a tabbed assembly should be tested against the actual material. A fit coupon is often cheaper than adjusting an entire batch.
Finishing
Decide whether the part will be painted, oiled, lacquered, laminated or left unfinished. Finish affects edge preparation, surface handling, visible tool marks and how parts should be protected in delivery.