Hypothetically Speaking...

Someone, or some people, from Seaford High School in Seaford, Delaware, presumably in the graduating class of '94, surreptitiously painted a giant "94" on the roof of the high school. Aerial photos of the giant rooftop "94" were published in the local newspaper, but the culprits were never punished. 20 years later, I'd like to postulate how, hypothetically, this could have been done.

You can't do this during the day. It must be done at night and you'd need three nights to complete it. The job is too big for one person reasonably, so it would require two malefactors.

First, measurements of the roof would need to be made. 1994 predates widespread use of the internet so Google Earth/Satellite-based measurements would be out. Sneaking satellite maps out of some secret agency would have been far riskier than a mission to measure the roof. If you wanted to get on the roof, the easiest way to do so would be to climb on top of the freezer outside the cafeteria and then make your way to the roof top. Trivial. Looking at Google maps I'd estimate the dimensions to be about 35x75 feet. Tools needed for the first night: tape measure. This would be a two person job for one hour, maybe less.

The measurements could then be laid out on graph paper, (computer aided design would have been beyond the dastardly miscreants' reach in 1994) and then reasonable dimensions could be made for the characters. The geometry of the roof would dictate that the characters be almost square rather than rectangular, so making it look "good" would be challenging. Geometry and trig would come in handy for scaling from graph paper and drawing a giant "4". The "9" presents a more difficult challenge, the round part is an ellipse, so you'd have to do a bit more algebra to calculate the foci of the inner and outer ellipses making up the "9" with the intent of using the "pins and string" method of drawing a 35 foot wide ellipse. I imagine making constant the ~7 foot width of the line making up the ellipse of the "9" would be challenging, skills that the perpetrator(s) may have picked up from Mrs. R.R or Mr. D.G in that very same building. Not a bad final exam given that so many school days were missed in the harsh winter that final exams were canceled for seniors that year.

After developing a reasonable layout on graph paper, measurements could be scaled up, and markings could be made on the roof using something like an upside down marking spray paint along with the "strings and pins" method of drawing an ellipse and using the same line for a giant straight edge. Tools needed for the second night: tape measure, spray paint, rope. This would be a two person job for two hours.

Finally, the criminals would have to figure out how to actually paint the "94" and paint rollers might come to mind. They might even have tried rollers and found that they get bogged down in the stones on the roof. From there they'd have to return to "Crime Central" and borrow something like an airless paint sprayer and extension cord from a now complicit parent who may have caught them returning to regroup. They would need a means to power the sprayer. They could take apart one of the ventilation fans and then access the power with a homemade version of something like this alligator clip to AC outlet converter. From there, painting inside the lines would have been a task probably picked up in kindergarten for at least one of the perps, maybe not both. Tools needed for the third night: airless paint sprayer, paint, alligator to AC outlet converter. This would take approximately eight hours, nearly all night during that time of year.

The rope used for the ellipse and straight lines could have been used to take supplies on and off the roof. Regrettably, it may have broken bringing down the only unused can of paint, leading to something less than a gallon of paint splattering on the grass outside of the back of the school by the tennis courts.

Shortly thereafter the offenders would probably have rented a skydiving plane with the door removed to get pictures of the giant "94" on film, that would then have to be developed and submitted on paper, by hand, to the Seaford Leader which doesn't even exist any more. My how times have changed.

All in all a lot of effort for a prank that hardly anyone saw directly and that in this day and age could have easily been faked by a 12 year old. It was also mildly audacious or perhaps foolhardy given that the police station was across the street. At the time the prank was heralded as anything from genius to heinous but the overall impact was minimal at most, but as Mr. B.D. said just before the class of 1994 shuffled out to get their diplomas we "put the 94 where Mr. Baltz could see it." I sure miss Mr. Baltz.