Don't walk them through, in or near long grass! Seriously, it is very difficult, and the grass seeds are barbed so they go in ok but catch on the way out and cannot be shaken out easily, so have to be removed by a vet. Luckily I have only ever had this happen once, and it was a week before my GSD was having his hips scored on his 1st birthday, so he had to have an anaesthetic to knock him out for the removal of the seed, and then again a week later for the xray.