1. The newspaper article was due no later than 4 o’clock and the editor got it in at exactly 3:59. He got it in right under the wire.
2. The deadline for applying to the university was the last day of March. Rachel procrastinated until it was almost too late, but then she stayed up all night filling out the application and got it in just under the wire.

Similar to: in the nick of time; down to the wire.