The rougher the surface the greater the nap. (depth of pile) With Pebblecrete use 15 – 20 mm plus, and with smoother finishes like Fibreglass 8 – 12 mm. Load the roller uniformly, not as shown below. A uniform load will allow you to get a better coverage. Don’t over fill tray, better to use about 1/3 of a mix at a time. Rough or uneven surfaces and internal corners cannot be easily painted with a wide roller. Usually 250 mm wide is enough.