Broadfork
In farming and gardening, the broadfork, also called a U-fork or grelinette, is a tool used to manually break up densely packed soil, like hardpan, to improve aeration and drainage.

It consists of five or so metal tines, approximately eight inches long, spaced a few inches apart on a horizontal bar, with two handles extending upwards to chest or shoulder level, forming a large U-shape.

The operator steps up on the crossbar, using full bodyweight to drive the tines into the ground, then steps backward while pulling backwards on the handles, causing the tines to lever upwards through the soil. This action leaves the soil layers intact, rather than inverting or mixing them, preserving the topsoil structure.

A broadfork can be used in a garden, or practically for one to two acres (4,000 to 8,000 m²). For larger areas, a tractor- or animal-powered chisel plow or similar tool is usually employed.

U-bar
A u-bar is similar to a broadfork, but has longer tines at 18 inches (or 457 mm) for deeper cultivation, since it is meant to be used in beds that have already been double dug at least once. A u-bar also has "elbows" that allow the tines to be raised above soil level when the handles are tilted all the way back.  Thus, clumps of soil that get caught on the tines can be broken up by shaking the handles up and down, rocking the tool on its elbows.

Whereas double digging a one hundred square foot (9.3 square meter) bed can take several hours, tilling the same bed with a u-bar can be done in 20 minutes.