Complex sentence: There are two general knife sheaths; one is flat with a spring retention and the other is tube-shaped and has an ajax triple thread, allowing the diver to insert the knife in it from any direction.
Split into simpler sentences: There are two general knife sheaths; one is flat with a spring retention and the other is tube-shaped and has an ajax triple thread. The latter sheath has a tube design, allowing the diver to insert the knife in it from any direction.