Coagulation: this is the name for the final blood clotting.
This is a complicated process (which will be discussed in the next page) in which, as the last step, fibrinogen is converted into fibrin.
The fibrinogen is already present and available in plasma and is soluble. Because of this coagulation step, the fibrinogen start to stick together into a mesh, a network, called fibrin. This fibrin is insoluble.
The fibrin mesh traps the platelets and other blood cells in the plug, and makes this plug very hard.
This is now called a (blood) clot.