What happens next in this paragraph?

How to measure for a storm door
Check for any obstructions.
Before you take any measurements, you should first have a quick glance around the doorway to check for any potential obstructions that would affect the installation of your storm door.
Look for the placement of door handles, exterior lights, the mailbox and even the doorbell.
In some cases these items may interfere with the installation of the storm door or prevent it from closing properly. If this is the case, you may need to relocate them or switch to smaller door handles.