Before you start, you’ll want to gather a tape measure, pen, and paper. It can be useful to have a helper too, especially if you have large windows.

Tip: To help you track dimensions and make other necessary assessments, download one of our measurement guides, like this one for the 400 Series.

You also need to understand a few different parts of a window before taking measurements. These include:

• Jamb: The pieces forming the top and vertical sides of a window or door frame.
• Head (or head jamb): The horizontal piece forming the top of a window or door frame.
• Sill: The horizontal piece forming the bottom of the window or door frame. Here’s the equipment you’ll need:

According to contractors, these cause the biggest delays. Blinds can take hours to remove, and window alarms will need to be removed before new windows are installed. Sometimes, it’s best to get your security company to help with disconnecting alarms.