Underframework

No. 2 shows the cop of weft in its case in position for working, where it is retained by two smooth bowls of bosses fixed in their places on the stand or underframework of the loom.

Source: wiktionary

And a dangerous extracurricular activity had helped turn his muscles to iron: he “rode the rods” with other boys, clinging to the underframework of Union Pacific freight cars rumbling through Abilene.

Source: wiktionary

He said at that time: I feel the deepest conviction that no sanitary system can be adequate to the requirements of the time or can cure those radical evils which infest the underframework of society unless the importance be distinctly recognized, and the duly manfully undertaking, of improving the social condition of the poor.

Source: wiktionary

As for the dedicated non-experts, they were moving again from urban detail to more general schemes of social regeneration, to the nature of what Sir John Simon had called earlier in the century the 'underframework of society', from issues related to municipal action within the particular city to national welfare policy which would iron out some of the differences between cities.

Source: wiktionary