Get rid of the grass and weeds that grow in the cracks of your sidewalk by spraying them with white vinegar. They should be dead by the next day and you can easily pull them out and throw them away. Be sure to keep the spray away from the areas where you want to keep the plants alive.You can also try sprinkling salt where you don't want grass growing.
Isn't it kind of tricky to use vinegar and salt because they spread out over time?
Do you mean the vinegar and salt become absorbed by the surrounding area where they are applied?
If so, the concentration of both the vinegar and the salt should become diluted enough over time where it does not harm anything except its intended target.