I do KWYM Sarah and Tegan, and luckily Jack's not a bolter, so I don't use one myself. BUT I know how easy it is with two to be distracted by the baby for just long enough for anything to happen to the toddler. If Jack was even a bit of a bolter I'd have to use one or I wouldn't be able to go out. It's just not worth the risk of something happening. I have seen it happen to others - one day I grabbed a little one who had bolted out of the supermarket while his mum was putting little sister in the trolley - there was a busy car park just outside the door. Luckily I grabbed him in time, but I saw how quickly and easily it happened.