A common assumption may be discerned in many of these inventions: if some part of you is too fat, it can be corrected by squishing. A program of aggressive squishing maintained long enough will cause the affected part to stay squished.
Our correspondents improved upon the original inventors’ ideas in all cases but one. No. 5 was not improved upon, because No. 5 cannot be improved upon.
No. 1 eliminates double chins, as “Mrs. Bat” correctly guessed.
Nos. 2 and 3 both correct misshapen noses, as more than one correspondent guessed. No. 2 appears to have minute adjustments, perhaps so you can specify the shape of your nose to match your favorite movie star’s; No. 3 involves quite a bit more of the head in the operation.
No. 4 is a rubber appliance for reducing and shaping the ankles. Fat ankles were a constant source of worry in the 1920s.
No. 5 is indescribably effective for pretty much everything, so any answer may be counted as correct. It is possible, however, that we are meant to infer more than the text actually states from the words that the advertiser set in bold. “The Natural Body Brace overcomes WEAKNESS and ORGANIC AILMENTS of WOMEN and MEN. Develops an erect, and graceful figure. Brings restful relief, comfort, energy and pep, ability to do things, health and strength. Does away with the strain and pain of standing and walking; replaces and supports misplaced internal organs; reduces enlarged abdomen; straightens and strengthens the back; corrects stooping shoulders; develops lungs, chest and bust; relieves backache, curvatures, nervousness, ruptures, constipation, after effects of Flu. Comfortable and easy to wear.” A brace that provides the ability to do things seems like a boon to humankind, and especially to women and men, who might like to do things together. How they work around the brace is not explained in the advertisement, but perhaps a diagram is provided with your order.
No. 6 shows both the Bust Reducing Bandeau in cream colored rubber (remember that this was the jazz age, when a flat chest was a desirable attribute for a woman) and the Neck and Chin Reducer. If the Neck Reducer is tight enough, it will probably lead to a rapid reduction in all other fatty parts of the body as well, solving multiple problems at once.