cam 20 has a through bore 25 which when aligned with the housing aperture 15 can be connected together by a pin 30 the pin connection allows bi directional movement of the unitary brake cam 20 as shown in fig2 fig1 and 2 also show that the brake cam 20 has an aperture 27 through which a workman 39 s lanyard can be attached the brake cam 20 has arms 40 extending to either side of the bore 25 normal to the axis of the bore 25 the arms are selectively articulable about the bore and can pivot into apposition with the bight 17 of the housing 10 to wedge the rope 50 against the bight 17 each of the cam arms 40 have a surface configuration 45 this surface is a rope engaging intaglio formation the rope 50 is an intertwined helix the arm surfaces 45 are a curved knurled intaglio image of the safety rope 39 s countour 50 thus when the arm surfaces 45 come in contact with safety rope 50 there is a marrying of the respective concave and convex portions of the two knurled surfaces fig2 besides showing the bi directional movement of the brake cam 20 also shows that the arms 40 are equidistant about the brake cam bore 25 to allow free movement of the safety rope 50 through the housing 10 when the cam 20 is in an unlocked position fig3 also shows from a plan view that rope 50 will be able to move freely through the housing 10 when the cam 20 is in an unlocked position fig3 and 4 accurately show the surface 45 of the cam arms 40 that form the curved knurled.