Spear
Spear is used for internally catching the tubular fish. Spear has a mandrel, grapple, release ring and nut. The mandrel has a tapered helix. Grapple has a matching surface. Turing left moves the mandrel down and places the grapple in engaged position. Grapple expands due to helical wedge surface on the mandrel and grips the fish from inside. For releasing, the spear is bumped down and turned to the right. This tends to move the grapple down and place it in release position.