to engage the distal end 182 in another of the slots 164 or 166 of the housing 160 having the key 180 engaged in the first slot 162 shown in fig3 a amp 4 positions the sheave 130 in its operating condition in this condition a tangential line running from the sheave 39 s channel 132 aligns with the stuffing box 39 s centerline so that the wireline 50 can be properly run into and out of the stuffing box 20 as shown in fig3 b the edge of the sheave 130 also fits adjacent the guard 140 affixed to the frame 110 in this position the guard 140 can prevent the wireline 50 from jumping out of the peripheral channel 132 of the sheave 132 when running the wireline 50 as shown in fig6 however rotating the hub assemblies 150 150 u2032 and fitting the key 180 in the second slot 164 on the outer housing 160 moves the sheave 130 away from the guard 140 this position provides clearance for rigging up the wireline 50 in the sheave 39 s channel 132 without having to remove the guard 140 which can be time consuming finally as shown in fig7 rotating the hub assemblies 150 150 u2032 and fitting the key 180.