This is an easy to make tool for driving a press fit oil pump pick up tube into the oil pump. It fits a 5/8" diameter tube, as used on many engines including the SBC up until they went to a larger tube in the mid/later-'90s. This particular tool is made from a 3/4" OD copper pipe nipple, other types of pipe may have a different OD to have a 5/8" ID so use whatever OD pipe you need to in order to have the correct ID.
The cut out allows the driver to be aligned with the hole in the pump. The edge of the tool registers on the raised lip that is on the pick up tube. The raised lip on the tube also acts as a stop for how far the tube is installed.
The hose clamp keeps the tool from spreading while the tube is being driven into place. It's a good idea to use Loctite 640 or similar sealer/locking compound. Be sure the pick up is in the right position to give the right pick up to oil pan clearance before driving the tube into place.
Wear eye protection.