To hold the centerline on the workpiece will help the device shown in the figure.
Recommend to read
“FLYING TANKS”
We are not talking about armored planes-fighter planes or combat helicopters, and about real tanks on the tracks. But with wings. It came up in the early 1930s, American designer Walter...
TEMPORARY! ON WEDGES
Not always rack shelves require a stationary position. Temporarily any of them can be attached using derevyannyh wedges placed in the gap between the flange and the wall of the Cabinet.