Random width is the combination of two or more widths of slate randomly installed to provide a "broken" or random pattern of key way spacing the side space between the slate in one horizontal course. Random width is most common on residential installations and tends to the more natural look.

Constant width installations are where a single width of slate is installed on the roof. In this case the key way spaces in alternate horizontal courses line up to create a more uniform pattern on the roof and provide a more formal style. Constant width is often seen on commercial projects, churches, courthouses, educational/ institutional buildings and large very formal residential projects.