Here, Bob Vila's YouTube channel helps you do something with joint compound. He could tell you what.
I first came across the site There I Fixed It via Metafilter, and then through the comments there, I found the Home Inspection Nightmares section of the site for This Old House, and then I spent about an hour there, looking at stuff like this home repair, which is — spoiler — not an approved use of a two-liter Coke bottle.
Both sites are lovely afternoon-brightening bursts of silliness. They will also make you want to be really careful about any homes you might purchase in the future, because people are not to be trusted.