'ParaLock Plotter', designed by David Young and manufactured in China for Weems & Plath Ltd (based in Annapolis, Maryland, USA). The plotter is made of acrylic and has two rulers that can be moved parallel to each other, with a locking knob to hold them in place. It has graduations in degrees along three edges so that it can be used as a protractor, and a ruler along the bottom edge (0-16 cm, divided to 1mm). The primary purpose of the plotter is to enable the transfer of GPS positions rapidly, easily and accurately to and from a paper chart.

The locking knob is covered by patent GB2426069. A secondary purpose of the design is to minimize the common problem of slipping of a parallel rule when it is stepped across a chart. This is achieved by the four finger holes in the rulers, these employ the fingertips to reduce slip and to feed back any accidental slippage to the user. This is covered by patent GB2426070.