In one of the passages following the party on Riverside Drive, a nameless, faceless male voice laughs and asks: "Burned any bras lately"? (3.5.1). For the feminist activists who really did burn bras in the 1960s and '70s, women's undergarments were useful symbols of patriarchal restriction and confinement. Sure, those suckers help to hold the girls in place, but they're also designed to make women's bodies conform to certain social conventions. And on top of all that, they pinch!
Thinking back to her young adulthood, the novel's omniscient narrator lists a stream of women's fashions that were designed for visual appeal instead of practicality or comfort:
Petticoats, waist-cinchers, boned strapless brassières with torturous nodes where the bones began or ended, modestly high-heeled shoes, double-circle skirts, felt appliquéd with sequins, bangle bracelets that always fell off, winter coats with no buttons to hold them shut, rhinestone sunburst brooches that caught on everything. (5.1.3)
Some of this stuff, like the waist-cinchers and boned brassières, could literally change the shape of a woman's body over time. Other articles are just useless. Question: who needs a winter coat that won't close up? Answer: someone who understands that she's supposed to be showing off the dress she's wearing underneath, and who laughs in the face of pneumonia, that's who.
Symbolic clothing appears a fair bit throughout the novel, like when Janet sifts through piles of gauzy, transparent garments with total confusion written all over her face (3.1.36), when Joanna shows up the party on Riverside Drive feeling ridiculous and uncomfortable in her poorly-fitting bra and pantyhose (3.2.1), when Jael dresses the other three J's in quarantine outfits that Joanna associates with burkas (8.7.1), when Anna is called "a monument of irrelevancy on high heels" (8.7.24), and when Natalie walks in with a tray of drinks, wearing scarlet, skin-tight clothing, no underwear, and Cinderella shoes (8.8.1). Make no mistake about it: the clothes women wear in The Female Man have a lot to say about the power of patriarchal conventions over their lives.