Copyright © All rights reserved. Made By Serif. The GM Capo TM FOR SQUARE NECK LAP STEEL AND HAWAIIAN GUITARS Home Understring Overstring Contact Using the GM capo as an understring type allows the left hand fourth finger to rest in a natural position behind the leading edge of the capo. This allows playing close to the capo without the fingers muting the strings. Use as UNDERSTRING TYPE (3/8 inch or 10 mm min string height)