I refused to believe my road worker father was stealing from his job.

This joke expertly employs the classic humor mechanism of wordplay, specifically a pun. The setup builds anticipation around the idea of a father secretly taking things from his workplace, which is already a relatable, albeit mischievous, concept. The punchline then delivers a clever twist by using a word with two distinct meanings to create a surprising and amusing image.

The core of the humor lies in the word "signs." In the context of the father's supposed thievery, "all the signs were there" initially suggests overwhelming evidence or indications of guilt. However, given that the father is a road worker, the phrase simultaneously conjures up the literal image of physical road signs – like stop signs, yield signs, or speed limit signs – being present at home. This unexpected literal interpretation of the idiom is what makes the joke land.

The humor is amplified by the common, lighthearted trope of people "borrowing" small items from their jobs, especially in professions where equipment is plentiful. The idea of a road worker taking home actual road signs is a wonderfully absurd escalation of this concept, transforming a simple idiom into a visual gag that tickles the funny bone without needing complex setup.