The fishing tool is the most widely used tool for overhauling oil and water wells. There are many varieties and specifications of fishing tools. According to the types of falling objects in the well, they can be divided into five categories: spear tools, overshot tools, junk basket, hook fishing tools, and cutter tools.
"Fishing Tools are classified as outside grappler, which surround the fish and grab it from the outside area and carry it up to the wellbore. Over shots falls in this category. The inside grappler is tapered in design with thread profiles which are able to move inside and thread the fish top enabling the fish to be recovered. Spears, taper mills fall in this category. Force intensifiers catch the fish on the top by means of pulling the fish. Jars falls in this category."https://www.petropedia.com/definition/1528/fishing-tool
Over shot is a very common fishing tool. The main fishing object is a smooth tube fish, which belongs to the external fishing type (i.e. catching the external surface of the fish).
Taper taps and die collars are common fishing tools for fishing the inner hole of the string. They are used for fishing the inner hole with holes such as tubing, drill pipe, casing milling pipe, packer, water distributor, etc. It is made of high quality alloy steel and specially heat treated. It has the advantages of high strength, high toughness and simple buckle making.