The really low rails do a few different jobs

a kill switch

The rocker is quite flat

you may pass a loop of the lanyard through the float hole and double back

while the stiffer blade provides maximum thrust for quick acceleration into waves

O'NEILL LENNOX SCALLOP 19" BOARDSHORTS - BLACK kanulock The really low rails doDESCRIPTION A durable stretch boardshort that's made to keep you comfortable in and out of the water. Quick dry, 4 way stretch fabrication is utilized for comfort and flexibility. O'Neill Men's boardshort 19" Outseam just above the knee fit 4 Way Stretch O'Neill Hyperdry DWR Anti rash hyperthread Scallop hemline Side pocket 90% Polyester, 10% Elastane