A drill pipe float valve is a check valve installed in the drill stem that allows mud to be pumped down but prevents flow back up. There are two types of float valves which are flapper type and plunger type.
The following VDO will demonstrate you the mechanism of each type of drilling float valve.
What is Stab-in valve and what are CLAMP ON CASING PROTECTORS ?
better with pictures
Stab-in valve is a safety valve used for stabbing in case of well flowing while tripping, running string, etc.
Clamp on casing protector is a casing protector equipped with handle. It is quick and easy casing protector tool.