under the wire

Example: “He handed in his application just under the wire.”

Origin: From horse racing, where a wire was stretched across the track above the finish line to give judges a fixed vertical reference for deciding which horse crossed first — a real practical necessity before photography could settle close finishes, since the eye needs something to align against. A horse that got under the wire had finished, and one that did so narrowly had finished by almost nothing. The phrase is American and early twentieth-century, and the same fixture produced "down to the wire" for a contest still undecided as it ends. What the idiom carries is not merely lateness but the specific relief of having cleared a hard boundary with no margin whatsoever.