Steel pipe blank flanges with tongue and groove face for PN 15.0MPa (150 bar)
join tongue and groove, in carpentry.
Integral steel pipe flanges with tongue and groove face for PN4.0MPa(40 bar)
They made joints in stone keeping the lintels in place horizontally using a tongue and groove joint and subsequently fixing the upright and lintel with a ball and socket joint or mortice and tenon.
Hubbed slip-on-welding steel pipe flanges with tongue and groove face for PN 5.0MPa (50 bar)