Because DaVinci Select Shake has a rib-structure on the underside, care must be used when installing Select Shake in valleys. Open or closed valley systems may be used with variants of each system. Whether installing an open or a closed valley system, valley metal can be made from 24" (610mm) stock of copper, minimum 0.5mm thick aluminum, or minimum 0.37mm width clad steel if you prefer to make your own. It is recommended to use self-adhered membrane in valleys if possible/available. Alternately, pre-formed ABS plastic or GRP valley accessories, available from most roofing retailers (both over-the-counter or online), can be used, as well as forming valleys out of lead (or lead substitute) in the traditional way. Note that for closed valleys it is best to use a Double "W" profile valley with Select Shake.