Rigging in a one-design class is often strictly regulated. Recently, the Laser Class changed one of the rigging rules regarding the hiking strap. The new language says “…the eye straps on the aft face of the cockpit may be rigged in any manner so that the hiking strap is fixed or adjustable and may include one cleat; one ring, thimble, or shackle; or both.”
The point of an adjustable hiking strap is to allow for more efficient hiking when sailing upwind and/or into the waves (usually more forward and straight legged) and when you are sailing downwind (usually sitting more aft and often with bent knees.)
There are no examples of changes given, so here is a short video from Steve Cockerill on what they have come up with using one jam cleat.