I think number 18 is an extremely important unwritten law, which needs more work during referee training. Never in 27 years worth of playing, officiating, or coaching. If I had, I probably would have needed CPR on the spot. Therefore, the attacking team asks for 10, the wall and restart then have to be managed. If no one asks for 10, then assume appropriate positioning on the field and maybe see a spectacular kick, or a great save.
Most HS fields are HS football fields and have markings.
Pretty easy for everyone concerned to see 10 yards.