A wooden model shows a throwing arm pivoting between two uprights, with a sling at one end and counterweight boxes at the other, beside its label. According to the label, the couillard (14th-16th century) worked like a balance with two movable counterweights, could fire up to ten shots an hour, throwing stone balls of 30 to 80 kg up to 180 metres, with an impact comparable to that of the trebuchet.