The cap the visible end of Porta Contours simple attach a dressed rectangular section (or DAR) of Tasmanian Oak or Pine. (Prime coat a piece of raw timber to apply to Pre-Preprimed Contours lining). The size of timber is a personal preference yet consider 21x21mm Tasmanian Oak (DAR2121TOSL27) or Pine (DAR2121PICL27) which will finish flush with the top surface of the lining.