They can be found at road junctions and at some roundabouts and there are no requirements for yellow box junctions to be accompanied by signs or a Traffic Regulation Order.
Gellir dod o hyd iddynt ar gyffyrdd ffyrdd ac ar rai cylchfannau ac nid oes unrhyw ofynion i gyffyrdd sgwâr ymddangos ynghyd ag arwyddion neu Orchymyn Rheoli Traffig.