This is one of the better entries in the "Lum & Abner" film series. Unfortunately, you really need to have lived through that era or else you need to be somewhat of a WWII era historian to appreciate much of the humor found here.
If you don't fall into either of those two categories, imagine Lum & Abner are the "Dumb & Dumber" of the 1940's. To help in the war effort, the government had put out a call to any and all inventors to submit their ideas to aid in the war effort. Through the daily "Lum & Abner" radio program, audiences knew that neither Lum nor Abner could come up with good idea if their lives depended on it. Could it possibly be that Abner has stumbled across a formula for synthetic rubber (which was a critical need during WWII)? Not only do Lum & Abner claim to know this vital secret, but before the film is over, all of Washington DC regards these two dimwits as home-spun geniuses.
For millions of Americans, the Lum & Abner radio program had made these two fictional characters seem like part of the family,... or at least part of your circle of close friends. They would take turns getting themselves into and out of trouble in such a way that you couldn't help but like these two well-meaning old geezers.
If you're old enough to have heard of BVD brand underwear, I'm betting that you'll get a real kick out of this film.