The Allen Pro Ratchet 50 helps you hold a sheet in position and adds friction whilst easing a sheet and features:

• internal ratcheting mechanism which only allows the sheave to turn in one direction
• 50mm nylon sheave
• on / off switch for the ratchet mechanism
• swivel head that can free spin or be be locked
• holes in the sheave centre for tying thru elastic.

See more info on the Allen Brothers website.