Current game stage: 1
Max Load of a material determines how much load (Mass) every side of it can hold. You can obtain this information using the Item Stats functionality added to the game in the alpha 7.6. To do this, place the mouse over an item to see the Object Stats, including its Max Load.
The function of Max Load is easily explained using an example.
Structural Integrity = Max Load ÷ Mass
In words: Devide Max Load by Mass of the block in order to get Structural Integrity.