Quilt is an old fashioned term used to describe the covering placed on top of the uppermost box. This barrier conserves heat and discourages the bees from building their nest up into the roof chamber and sealing the weather-proofing lid on, and was once made of cloth or Hessian. Also known as a 'crown' board or 'cover' board they are now generally made of wood, which has the advantage of being more durable, not providing a home for wax moth larvae, being easier to prise off, and which can be cleaned and sterilised. Many modern crown board designs may also be multi-purpose, designed to facilitate feeding, clearing, or swarm control for example. Glass models are available, although these should be removed in the winter to avoid water condensation dripping back onto the winter cluster.