It allows you to raise your motor on the transom (change the x-dimension). More types are available (fixed or adjustable while you run), here's one:<br /><br /> http://www.spidybot.com/prop/prop_051.htm
The one mentioned moves 12" so by putting it low enough you'd be able to lower the motor.<br /><br />Think about it - your motor will end up sitting pretty close to the water.
