Broadfork

The broadfork, also called a U-fork or grelinette, is a garden tool used to manually break up densely packed soil, including hardpan, to improve aeration and drainage.

[1] Broadforks are used as part of a no-till or reduced-till seedbed preparation process because they preserve the soil structure and avoid the resurfacing of weed seeds.

This action leaves the soil layers intact, rather than inverting or mixing them, preserving the topsoil structure.

[3] A u-bar is similar to a broadfork but has longer tines - up to 18 inches (46 cm) - for deeper cultivation, since it is meant to be used in beds that have already been double dug at least once.

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.