I have never used weed killers. A probably irrational horror of chemicals.
Anyway I have a small area of cobbles, stone sets set in sand (no cement
between or below) and I have been persuaded that a weedkiller may be the
best way to clear the large amount of grass and weeds coming through the
gaps.

I think I have heard that the right chemical will leave some attractive moss
growing but kill the leaved plants. What would that be? The cobbles are
constantly crossed by pets and humans so there is considerable danger of
getting it indoors on the carpets and cats eating it. But I could make sure
the pets didn't go on it for a while.

Tim w