A couple of weeks ago I did a job for a fairly famous young photographer who lives and works in a studio downtown. I knew he was a photographer and had heard he was well known, but to me he was just a guy who needed some work done.
There was a bunch of stuff, hanging new Levalor shades in his apartment, which is upstairs from the studio; fixing a ceiling fan, building drawers for a custom built captain’s bed. Whoever built the bed forgot to put drawers in it.
There were some minor things to do in the office/studio on the floor below, as well. The biggest thing to be done there was to re-install the 1400 BTU air conditioner in the large window of the office.
Again, whoever installed it did a half-assed job.
The air conditioner was tilted out and downward at a 30° angle, resting on a plastic milk carton on the wide ledge in front of the window. The plastic accordion assembly, the part that fills in whatever part of the window the air conditioner doesn’t had been bent outward to accommodate the angle (proper angle is 5-7°) and whatever space left over was covered by copious amounts of duct and masking tape. I would have been embarrassed to leave an A/C in a window like this.
You need a slight tilt to let the water that condenses on the grills drain out towards the street, not onto your sill. I’ve seen a lot of ruined windowsills because of an improper installation. But 30° is just past ridiculous.
I learned how to install A/Cs many years ago when I first started working at the building I worked in for 17 years. A tenant was trying to bypass the building Super and/or handyman who were asking $50 per unit to do a proper installation. I said I would do it for $30. This was 16 years ago, mind you.
I told the super and handyman, and to my surprise they said it was OK for me to do it.
“But you have to do it our way,” said Randy the handyman. Randy was a slight effeminate man with a neat little goatee and pencil mustache. He proceeded to show me how they wanted the installation done, using a steel “L” bar, Plexiglas, and silicone in lieu of the plastic accordions that come with most A/Cs.

This thing is like a sieve.

You have to remove the metal catch bar on the top of the A/C and replace it with the L bar, which is cut to the exact width of the window frame. There are notches cut at either end of the bar so it will fit into the open window, the un-notched part of the bar will hold the unit against the frame. Properly done it is impossible to drop an A/C out of the window. After you attach the bar and seat it in the window properly, you measure the open spaces on either side of the unit and cut your Plexi to the proper size, then secure them onto the window frame and bar with silicone.

I scratched the Plexiglas with sandpaper to make it hard to see in.

This makes it airtight and water tight, something an accordion cover is not. If you leave your A/C in the window year round with those things I guarantee you either freeze your ass off or have the things covered with towels and duct tape and such as the cold air just whistles right through all of the gaps.
I’ve seen some other things used as well, like pieces of cardboard, wood, and shoeboxes.
Here’s my across the alley neighbor’s Nike box covers. Tacky, tacky, tacky.

This is my installation, and this is the way all of my installations are done, neatly.

Over a month ago I did an A/C swap-out for one of my regular clients, The Center For Fiction. It was an over the window mount, and it was a big 30,000 BTU monster that had to weigh 100 pounds. I hired a guy from the task rabbit Facebook page to help me, I knew there was no way I was getting the old one down and sliding the new one in alone. The guy that showed up was thankfully 6-foot 3 and almost 300 pounds. He was very strong and we got it done without a lot of hassle. But I do most of the installations alone.
I’ve done dozens of A/C installations, and I’ve gotten good at it. When I worked at the building, at some point in the early 2000’s, a memo came down from somewhere up high: Rudin employees were forbidden to do any more A/C installations. This was because a building super had dropped one out of a window at one of our fancier buildings on Park Avenue. It turned out that it was the slight, effeminate Randy, who at 28 had become the youngest building super in Rudin history. He kept his job, and there were all sorts of rumors as to how he managed to do that, but he ruined a good source of easy cash for the rest of us.
Not that the memo really stopped anyone, supers and handymen still do it for tenants they knew and trusted.
Everyone else had to hire one of only three air conditioning outfits that had the proper 5 million dollar liability insurance. They all charged around $100 a unit if not more. And a lot of them did some pretty sloppy installations, some not even bothering to remove the bracket bar from the A/C, resulting in a less than 5° tilt, or no tilt at all, ruining more windowsills.
When I was still a doorman one of the tenants decided to put his own air conditioner in the window one hot night in August. He came home after midnight and opened his window and tried to seat his A/C. It fell out of the window, and he instinctively grabbed the power cord. This caused the errant A/C to swing through the window of the bedroom below, scaring the shit out of the couple in bed there and showering them with shards of glass. Luckily no one was hurt.
This apartment faced the courtyard, and the A/C would have just fallen onto concrete and not hurt anyone. It fell anyway after it broke the window.
So remember folks, if you don’t know what you are doing, or if you want a really tight, neat looking installation, call a pro like me to do it. It still gets hot in September.