"Double underhand" – the style where the bar is grabbed with supinated wrists (palms look at the face) and bent over ring and little fingers with ulnar deviation of wrists. This style has two variations – strict and modified.
1) Strict DU is performed with pads touching in the middle, distance between pinkies is about 1”-1.5”, to avoid smashing finger knuckles into each other. The bar is pressed down with tricepses and lats, wrists work on ulnar deviation in static mode.
2) Modified DU is performed with pads moved to the end, about 1.5”-2” of the pad are on the bar. In this case the assistance of pectoral muscles is included. The main force – is big axle pressure, then when the bar is properly loaded, wrists give downward ulnar deviation hit, which folds the bar.