Outer membrane β-barrel proteins (OMPs) form cylindrical structures that function as pores, substrate specific transporters, and membrane plugs. The structural stability of a β-barrel protein is largely dependent on the interactions between neighbouring antiparallel β-strands. Previously, we characterised one such interaction, the mortise-tenon joint. Formed from the interaction between a luminal aromatic residue on one β-strand and a glycine on the adjacent β-strand, mortise-tenon joints were shown to contribute to the folding and stability of the Pet autotransporter β-barrel. Here we survey the prevalence of these mortise-tenon joints in all OMP structures. The unique 60,90 chiral 1 and 2 angles, which are a definitive feature of the tenon side chains, were used in conjunction with a glycine-aromatic proximity analysis to screen the Protein Data Bank for tryptophan, tyrosine and phenylalanine tenon joints. We present the structure of the Pet autotransporter beta-barrel, structural analysis of previously characterised mortise-tenon joints confirmed their presence and unique chiral angles in the Pet barrel. We also used the OmpF β-barrel as a system to confirm the presence of three predicted mortise-tenon joints. Wild type and mortise-tenon joint mutant variants of OmpF were refolded and analysed using circular dichroism and thermal melts to determine the role of mortise-tenon joints in OmpF. Our results are discussed in relation to the structural requirements of OMPs and the possible role of mortise-tenon joints in β-barrel stability. Understanding of inter β-sheet interactions and their role in β-barrel stability is also important to the rational design of synthetic β-barrels.