Allotment ground preparation on a new and an existing plot often involves removal of stones from the soil. One of the best tools for this is the sieve, sometimes called a riddle. The basic sieve is a wooden or steel circular frame with a mesh fitted to the bottom.
Sieves can be used to sieve you compost before potting up seedlings, passing the compost through the sieve removes any large lumps that will create voids in the pot. Voids in the pot will inhibit root growth.
Riddles and Sieves have various sized holes to suite the purpose you have.
Mixtures of soil and stones are passed through the sieve giving a pile of soil and all other material like stones larger than the hole size is held in the frame.
When choosing a sieve the prime consideration is the size of stones you would like to remove.