As we have seen, Boneh includes the prohibition of leveling the ground, whether in order to make it easier to walk on, enable chairs and benches to be placed upon it, or to build upon it. Therefore, one who levels a mound of earth or fills in a hole transgresses a Torah prohibition.
If a yard was flooded by rain, one may not spread sand or gravel over it in order to cover the mud. Since those materials are normally left in the ground, this is considered leveling the ground, a violation of Boneh. However, one may spread straw that is designated for animal food over the mud, since he does not intend to leave it there. This is on condition that the straw is spread with a shinui, such as using the back of a shovel to distribute it. Otherwise, the act of spreading looks like a weekday activity (Eruvin 104a; SA 313:10).
One may cover excrement or saliva with sand, since one who does this does not intend to improve the yard, but only to cover the filth (Beitza 8b; MB 313:55). Similarly, if oil spilled on the sidewalk or the floor, one may cover it with sand to prevent people from slipping. This is on condition that the sand was designated for this purpose and thus is not muktzeh (below 23:3). One may similarly spread salt on ice in order to prevent people from slipping (SSK 25:10).
One may not sweep the yard lest he level indentations and thereby transgress a Torah prohibition. However, if the yard is floored with tiles or pavement, he may sweep it.
One who has clay stuck to his shoes should not try to rub it off against the ground, because he may end up leveling the ground (SA 302:6). Some are not worried about this possibility, and permit rubbing off the clay (Rema, Taz). One who so wishes may be lenient, but it is preferable to be stringent. In contrast, one may rub off the clay against a grate, tiles, or stones even le-khatĥila (MB 302:28).
One should not rub saliva that is on the ground into the dirt with one’s shoes, to avoid leveling the ground. If one finds the saliva disgusting, he may step on it in the natural course of his walking, as long as his intention is not to spread it and level the ground (SA 316:11).
One may not play marbles on the ground lest he level the ground so that the marbles roll smoothly. Similarly, one may not play any game on the ground that requires completely flat ground, lest he end up leveling it. Even if the ground is paved, one may not play there, as there is a concern that one might then end up playing on unpaved ground (SA 338:5 and MB ad loc. 20; MB 308:158). However, one may play on the floor inside one’s home; since all homes today have flooring, we are not worried that, as a result of playing there, anyone will end up playing outside on unpaved ground (SSK 16:5).
Children may play in a sandbox containing fine, dry sand, for as long as the sand is dry, the sand will pour back into any indentations made. However, if the sand is wet enough to make holes in it, one may not to play with it (MB 308:143). Wetting the sand is also forbidden, as it constitutes Lash (MB 321:50). If the sand has not been designated for play it is muktzeh, and thus playing with it is forbidden (SA 308:38; MB ad loc. 144).