On a free kick, opponents must “respect distance” by being at least 10 yards away from the ball. A kicker who thinks they are too close can “ask for 10” from the ref, who may then move the opponents back.
Sometimes an opponent stands right in front of the ball, like 1 yard away, making the kicker ask for 10. That’s not allowed — the opponent isn’t “respecting distance,” and is killing the kicker’s chance for a quick kick. A ref could caution (yellow card) the opponent.
As a ref, before games I like to ask players, especially at U12 and U14 levels, if it’s OK to stand 1 yard away and make the kicker ask for 10. More than half say “yes, that’s OK.” When I tell them no, they often say “But coach taught us to do that!”. I give the coach a smile, maybe a “naughty you” finger wave, and remind players they could get yellow carded, especially if taking away a quick kick.