Right hand helix has the thread that advances in the nut when turned in a clockwise direction. When thread advances in the nut when turned in an anticlockwise direction then it is termed as left hand helix thread. ... It is also called an American thread or Unified thread.

Acme thread is a modified form of square thread.

Mechanical seals are used to prevent leakage.
A mechanical seal is a device that helps join systems or mechanisms together by preventing leakage (e.g. in a pumping system), containing pressure, or excluding contamination. The effectiveness of a seal is dependent on adhesion in the case of sealants and compression in the case of gaskets