We have a "round pen", OH built it. It is all wooden and looks great, apart from all the weeds growing in it at the moment. We use it for loose schooling and it is a godsend in the winter when the paddock is too wet, they get to go in the pen and have a blast and a roll and are then happy to go back in their stables. Would be lost without it in the winter to be honest but don't use it much in the summer unless we have a youngster in that needs some work. Great for backing too as it is a safe confined area.