The Scissor Truss is one of a number of trussed rafters which incorporate a vaulted ceiling into their design. Others include the Gambrel Truss and the Raised Collar (or Raised Tie) Truss.
A vaulted ceiling is a nice way to add character or interest to a room. It can make cramped, low buildings feel airy and light. The ceiling pitch can be used to accommodate roof windows. We find scissor trusses are used frequently in extensions and conservatories.