“D fence” signs are popular at football and basketball games The letter “D” and a picture of a white picket fence spell “defense” and are displayed by stadium fans when the home team is on defense. The “D” and “fence” have also appeared on many gift items, such as T-shirts.
 
Lorin “Big Lo” Sandretzky said that he invented the sign and first used it at the Los Angeles Raiders-Seattle Seahawks game in Seattle on December 22, 1984. The sign has also been popular at New York Knicks basketball games.
       
 
New York (NY) Times
SEAHAWKS STOP RALLY BY RAIDERS
By MICHAEL JANOFSKY, Special to the New York Times
Published: December 23, 1984
SEATTLE, Dec. 22— With one of their best defensive performances of the year, the Seattle Seahawks today ended any thoughts of the Los Angeles Raiders repeating as Super Bowl champions.
 
With unrelenting pressure from their defensive line and swarming coverage by their secondary, the Seahawks allowed the Raiders to cross midfield only three times and beat them, 13-7, in the American Conference wild-card game.
 
6 November 1994, Syracuse (NY) Herald American, pg. A12, col. 2 photo caption:
SU FANS HOLD a “D Fence” sign up during the second quarter of the game.
 
Ballard (WA) News-Tribune
Another side to Big Lo
By Joy Henley
02/01/2006
Even if you do not recognize Burien’s Lorin Sandretzky by name, it is likely you have seen him.
(...)
Just call him “Big Lo;” everyone else does.
 
Big Lo invented the “D Fence” sign that is popular throughout the nation—the letter D held alongside a picket fence.
     
Bread City
February 11, 2008
THE FIRST D-FENCE SIGN
I used to have a football blog, but I gave up on it after last season. It’s just been sitting there, catching crazy page hits and comments on two-year-old gambling picks, so I decided today to shut it down. But there is one thing I had to salvage, an interview with the guy who claims to have invented the D-FENCE sign. This was originally published in September, 2006.
 
The first time I ever saw a D-FENCE sign was during a Knicks game in the 1996 NBA playoffs. It was so popular with fans during that series, the two guys who brought it to the games were interviewed on television as the sign’s creators. Lorin “Big Lo” Sandretzky says that these guys are liars, because he made the very first D-FENCE sign in 1984. Here’s what he has to say.
 
Where did the D-FENCE come from?
 
BL: I was walking home from school with my friend, and there was this piece of picket fence that had broken off next to the drug store. The DE-FENSE chant had always been popular at ball games, and my friend and I just looked at one another, and said “D-FENCE!” It was a joke, but that’s what gave me the idea. Then that weekend, I stenciled out a cardboard D and a piece of cardboard fence, and I brought it to the Seahawks v. Raiders game. The first time people saw it, everyone was like, “What’s with the D and the fence?” I was a senior in High School at the time.
   
Google Books
100 Things Knicks Fans Should Know & Do Before They Die
By Alan Hahn
Chicago, IL: Triumph Books LLC
2012
Pg. ?:
The chant became a regular staple at the Garden, with fans getting creative to the point where one would hold up a large D and another would hold up a section of picket fence and run around the concourse that separates the upper and lower bowls of the arena.
 
YouTube
Game Day D-Fence Sign
About.com
Published on Feb 1, 2013
A D-Fence sign is a popular way to pump up the crowd during a game. This video from About.com has a quick guide to making the classic D-Fence sign.