Gaskets are to be used to fill space between flanges. Gaskets are to be made of metal, rubber, plastic, paper, or some kind of goop - do not use cow or sheep manure. It cracks when it gets dry. All bolts must have a head on one end and a nut on the other. All piping must be installed with valves.
Gate valves have a gate inside.
Glove valves have a glove inside. Check valves have a check inside. Angle valves have an angle inside. Plug valves have a plug inside. Diaphragm valves have a diaphragm inside.