Reply by JayT

or more simply it s just a matter of using tenon joints instead of screwing things together like in the first pic?

thanks,

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This. A well fit mortise & tenon joint is extremely strong in multiple directions and does an excellent job of resisting racking forces. Now take a horizontal M&T joint for the stretchers and combine with a vertical M&T joint from the legs to the top and you have increased the rigidity exponentially because of the different directions.

-- https://www.jtplaneworks.com - In theory, there is no difference between theory and practice. In practice, there is.