Handy stuff, those rolls/mats of 'grass'. It's also available as a 'hairy mat', the 'static grass', already glued to the backing, which stands up like blades of grass. On both versions, if you want to make bare patches, just dampen the required areas and scrape off the 'grass' - keep this, as it can be used to simulate rough patches, weeds etc. The bare areas can be painted and textured as required.