An apparatus for removable insertion into an excavated trench to protect a worker against collapse of the trench wall, which is often termed in industry as a trench shield or cage or box, comprises cross members interconnecting opposite sides of a protective peripheral wall that are in the form of rounded annuluses. Additional members are provided to interconnect adjacent pairs of annuli which are spaced one from the other in a height direction of the wall. This forms an interconnected internal frame of the apparatus which primarily provides compressive strength of the apparatus against collapsing of the trench wall instead of the protective wall so that the protective wall may be made to be lighter in terms of mass. Further, the protective peripheral wall forms a tube substantially fully enclosing a working area defined by the wall.