The spud wrench was originally used to remove a piece of piping called the "spud" on old toilets. The spud wrench fit over the spud nut. As of 2010, the spud nut is no longer used on modern day toilets. The tool kept its name, however, and has since gone on to find uses in other trades.
Construction workers that work with large metal construction beams or large piping use the iron workers spud wrench to line up the connection holes. The steel beams have holes in the end to connect the beams together. The pointed end of the spud wrench is put through one hole and moved around until the second beam is in the proper position. The end of the spud wrench will go through the second hole. The spud wrench is removed and the beam is bolted into place.
Steamfitters and pipefitters use the spud wrench in the same manner. Large flanges and large pipes are aligned by the pointed end of the spud wrench being placed through the first hole. The steamfitter or pipefitter knows when the second piece of pipe or flange is in the proper place because the handle will slip through the second hole.
The spud wrench and adjustable spud wrench can be used to tighten nuts and bolts. The spud wrench must be used on the correct size nut or bolt. A full set of spud wrenches will provide a broad array of bolt or nut sizes that can be tightened. The adjustable spud wrench adjusts like a crescent wrench and can be used on any nut or bolt that will fit in-between the spreading distance.
The pointed end of the spud wrench can be used as a handle in jacks. Pipefitters use the spud wrench handle to jack up hydraulic jacks while they are trying to align a flange to a piece of pipe. The spud wrench is part of the tools a pipefitter carries. A jack handle is an extra piece of equipment that would need to be carried to the work site. Using the spud wrench saves time and the hassle of carrying an extra tool. It is always available in the case of an unforeseen need for using a jack while doing a job.