The C trim is usually fitted into a bed joint of the brickwork or a 35/50mm (depending on the trim type) deep chase cut out with an angle grinder fitted with a mortar chase disc. Apply polyurethane adhesive to the back of the C trim every 300mm. Fit the trim into the slot and press firmly back to the wall to overlap the D trim. Apply a clear silicone sealant along the length of the trim into the slot to seal the trim in. A smooth finish can be obtained by wiping the sealant with a moistened finger.