A football team that is “knocking on the door” of a touchdown has the ball deep into the opponent’s territory, usually within the 20-yard line or the 10-yard line. The “door” is the end zone. “Dartmouth had been knocking on the door of a touchdown or at least a goal from the field” was cited in print in October 1924.
5 November 1923, Biddleford (ME) Daily Journal, “Biddleford High Outclassed Bridgton Academy and Won 19 to 7 at Prospect Park,” pg. 3, col. 3:
The Biddleford team showed more strength than the score indicated, as they were knocking on the Bridgton door late in the first half, and withonly a yard to go for a first down a Bridgton forward pass was intercepted.
26 October 1924, The Sunday Herald (Boston, MA), “Eddie Dooley is hero as Dartmouth gets 6-0 victory over Harvard,” sec. 2, pg. 1, col. 7:
Already, you know, Dartmouth had been knocking on the door of a touchdown or at least a goal from the field.
2 December 1934, Morning Advocate (Baton Rouge, LA), “Colgate Tactics Used To Produce Dramatic Finish,” pg. 2, col. 6:
The Bengals came right back after that and were knocking on the door.
5 October 1941, Boston (MA)
The Cadets were knocking on the door of another tally when the game ended.
Google News Archive
29 November 1942,
Just before the eriod ended, thanks to a 43-yard run by Ben Martin, Navy was knocking on the door again, reaching the Army three.
Google News Archive
3 November 1946, Eugene (OR)
Before the opening quarter ended the Bruins, after another pass interception, were knocking on the door from the Saint 8-yard line.
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New York, NY: Random House
With only two minutes gone in the final period, the Rams are knocking on the door.
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Atlanta, GA: Gridiron Publishers
Sparked by a Pettus run of 17 and a tremendous catch by Lauder of a Wood pass, Auburn was knocking on the door with a first down at the Alabama two.
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St. Lucia, Queensland: University of Queensland Press
The Armadillos were knocking on the door all third quarter but only came away with a field goal, and now it’s Hope’s chance to steal the ball game.
By Tiki Barber and Ronde Barber with Paul Mantell
New York, NY: Simon & Schuster
Early in the fourth quarter, they marched eighty yards on the ground, and were knocking on the door again with third and goal to go from the eight yard line.
My Faith and the Tackle That Changed My Life
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We fell behind 17—13, but we were knocking on the door at the 6-yard line midway through the fourth quarter.