The traditional material used for Finnish knife handles is curly birch. The material comes from the curly birch belt in Central Finland. The blaze-patterned curly birch is an excellent fit as a material for a knife handle, because it's durable and fair. This beautifully patterned curly birch is available on the market in limited amounts, which makes the price notably higher than regular birch.

The leather sheaths of Marttiini knives are made with either vegetable or chrome tanned oxhide. The leather hides are purchased from both Europe and South America. The sheaths are made with both dyed and natural colored leather.

The knife sheaths are still made mostly by hand. Each sheath has to be exactly the right size and shape, so it forms a fitting pair with the knife. A section of the leather is cut with a model iron, and the seams are attached with glue before sewing. Most sheaths have a plastic piece inside that supports the sheath and protects the blade.

The printing on the sheath is made on either the cut section or the finished sheath. Rivets, and in some cases a bronze collar, strengthen and adorn the sheath.