its very simple, look at the tv and internet video showing them placing plywood behind the shower panels first. THIS SHOULD BE CEMENT BOARD OR A MOSIURE BARRIER WATER RESISTANT PRODUCT not plywood that absorbs water and can expand and cause damage to the shower lined walls. they do this to save money and time. plywoods cheap and using it saves on labor because cement board requires more hours to complete job based on applying it properly????? User's recommendation: look elseware.