When you do not have a suitable spanner to Unscrew the hex-head bolt will help out any screw with two nuts — preferably square-shaped.
Recommend to read
MIRACLES FROM “ARMSTRONG”
We left sir William Armstrong and his designers, who belonged to the elite of British shipbuilding, at a time when the firm appeared on a wide road. After the completion of the new plant...
ELLIPSE-PANTOGRAPH
In the modeling practice is often necessary for the creation of ellipses of various sizes, with different ratios of semi-axes. There are several ways of constructing such figures. But...