The phrase "hollow log" refers to a tree trunk that is empty inside. It can also be used to describe something that appears full or solid on the outside, but lacks substance or depth.
Sentences with «hollow log»
Shake Rag Hollow and Thumpin» Dick Hollow, just down off the escarpment, were places where you waved a handkerchief or thumped a hollow log, respectively, to summon the local moonshiner. (si.com)
Esposito raised the level of difficulty through several tests, ultimately hiding the Cheetos inside a hollow log. (sciencedaily.com)
The den can be a hollow log, a rock shelter, an old rabbit warren or similar. (icn2018.com)