0 comments Details & Options frame & apron On this page you will find some of the commonly used terms and descriptions to help you finalise your ofuro order. 1 – PLANK EDGE The 42mm thick hinoki slabs are joined in such a way that the more permeable head of the plank is completely protected. 2 – KAMACHI (BORDER) EDGE For tubs wider than 800mm, it is necessary to strenghten the top with a 60mm thick frame (kamachi). 3 – COPPER APRON Traditionally a copper apron is applied on the bottom to protect the side of the bottom plank. It has 2 functions: avoid water to penetrate the wood perpendicular to the grain the copper oxyde has a fungicidal action. 4 – NO APRON For a lighter, more natural look we can treat the bottom plank head with natural oil by Kreidezeit. In modern bathrooms this area is not so severely exposed to rot like it used to be in ofuro of the past.