The following description is taken from The Journal of the Institute for Hacks, Tomfoolery, and Pranks at MIT.
When the Harvard Bridge was closed for renovations in 1924, 1949, and 1986, proposals were submitted to rename the bridge for MIT. Each time, however, the proposed name change did not make it through the long political process required. Many at MIT, feeling that the bridge was poorly designed, did not want it name for MIT.
While the Harvard Bridge was closed in 1949 for renovations, the "Harvard Bridge Closed" sign was replaced by Tech students with a sign saying, "Technology Bridge Closed." At the opening ceremony later that year, Massachusetts Governor Paul A. Dever led a motorcade toward the bridge. Just before he reached it, a convertible containing ten members of The Tech staff, a brass band, and two clowns pulled in front of the governor's limousine and started across the bridge. The police stopped the convertible, but the pranksters' car was the second to cross the newly rebuilt bridge.
The official length of the Harvard Bridge is 364.4 Smoots plus one ear. Distances on the bridge are indicated with a colored paint mark every Smoot and a number every ten Smoots. Biannually, the pledge class of Lambda Chi Alpha repaints the markings with a new color. The police have come to accept the Smoot marks. In fact, they use the markers to indicate locations when filing accident reports. After the bridge was rebuilt in the late 1980s, the Smoot markings reappeared and the tradition continued.
The story of these markings as told by Oliver Reed Smoot, Jr., '62:
As all who walked the bridge in those days will remember, it was difficult, especially in the rain, sleet, snow, and fog of which Boston gets its share, to know how much further you had to go to get to the Institute. So in October 1958, O'Connor...devised the idea of marking off the bridge in pledge lengths. Scanning the assembled pledge class, he determined that I had the short end of the stick.
As with many pledge tasks, there was an easy way out if a little ingenuity was exercised--namely, use a string. In any case, Pete, Gordon, Nate, and Bill agreed to help and we set off with the paint, chalk, etc. Unfortunately, a brother in the class of '61 thought this task was so hilarious that he accompanied us. With him there, we had no choice but to do the actual measurements. I can tell you that even then I could not do the equivalent of 365 push-ups, so much of the way I was carried or dragged.
Luckily for the five of us, we were cold sober; in any case, when an MDC [Metropolitan District Commission] black van appeared at about the 300 mark, we cut fo the dark recesses of the Great Court and waited for them to leave.