To protect the legs of a cultivator or plough from damage, many machines will have shear bolts. These bolts pass through the leg and frame of the machine and are designed to snap when the legs come in contact with a rock or other unmoving object. The idea behind this is to save the frame and leg from bending, using an incorrect shear bolt and result in the bolt not shearing and expensive damage occurring to the machine.
There is a huge range of cultivators available, mostly cultivators are designed with a tillage system in mind. Starting from a minimum tillage system using machines like the straw rake, you can go to the other end of the spectrum to a heavy cultivator like the Sumo Trio. One of the most popular cultivators of recent times has been the short disc. Machines like the Simba X-press and the Vaderstad Carrier are an excellent all-round light cultivator which are equally adept straight onto stubble or breaking down ploughing.