external fixation assemblies are provided which include a frame having one or more structural members for connecting to rods adjustably coupled thereto to provide a plurality of fixed positions around a patient &# 39 ; s bone . the arcuate members include a plurality of locating indicia which can provide a physical contrast to a remaining surface of said structural members when exposed to x - ray radiation . this invention also provides protruding lug portions on arcuate structural members to increase compressive forces during patient treatment and a marking system for identifying openings in structural members during treatment .