The Sabbatical Year

1. During Shemittah one may not clear a field, neither of big or small stones, whether in one's own field or that of a friend, since this is considered to be preparing the land for sowing and planting.
2. If, for example, one requires the stones for construction and one's intention is not for agricultural purposes, one should remove only the top layer of stones, leaving in the earth those stones that are attached to the ground. In this way it will be clear that one's intention is not for agricultural purposes.
3. However, a contractor who erects buildings may take all the stones and does not need to leave the bottom layer, since his profession is proof of the fact that his goal is to use the stones. Even today when it is no longer routine to take stones from a field for building purposes, rather one uses stones hewn from a mountain quarry, he may still remove stones from a field.
4. One may remove stones from a parking lot, playground, path or similar expanse. Similarly, it is customary to weed wild grass that grows in gardens and empty lots so it should not serve as a hideout for snakes, or in order to prevent fires. This may be done during Shemittah but one should not uproot them with their roots. Rather one should only cut off what lies above the ground. If for some reason one does have to remove the roots, one should do so by hand and not with a hoe.
5. Taking stones from a fence that is higher than ten tefachim: If the fence is made up of more than ten stones, each weighing the equivalent of two human beings, one may remove them. If the fence is lower than ten tefachim, contains less than ten stones, or is made up of small stones that weigh less than two people, one may take them all besides the lowest tefach.

   When taking stones for building purposes, it must be clear that one's intention is not to benefit the land, for example he can be seen taking the stones to a nearby building site. In absence of this condition it would be prohibited on account of mar'at ayin.

6. It is common practice to gather small twigs and straw for barbecuing in a garden or forest. This is permissible during Shemittah. There is no need to fear that one will be suspected of gathering the twigs for the sake of improving the land, since the barbecue is proof that one's intention is to light a fire.

For any questions in practical application of these halachot, please consult a rabbinical authority.