Having an air conditioner in the hot summer heat is a must, but you have to make sure you install it properly. Window air conditioners can immediately become a safety hazard if you don’t place them in your window securely. The biggest fear is that they will fall out of the window and break something, or even worse, hurt someone. So you have to take steps to make sure they are going to stay right where they are.
When installing the air conditioner, the first thing you should do is make sure there’s no extreme tilt. If there is, that means you need to place something else underneath the back side of it to prop it up so it won’t slide. You can cut a piece of wood the proper thickness to prop it up, or buy an AC bracket that can screw in and become a stable panel on the under side.
After you place the A/C so it is stable, pull out the sides to expand to the width of your window. You can then close the window on the A/C. It is smart to place brackets above the bottom window to keep the vibration from sliding it further open. If you have gaps between the top and bottom, there is foam insulation made specifically for that, which you can get at any hardware store.