If you have a wooden garage door rip off the nailed rubber seal.
How to cut garage door seal.
Square cut the pvc do not miter and use the utility knife to cut the vinyl flap the same length as the pvc portion of the weather seal.
New weatherstripping comes in rolls and you can easily cut it to length with a utility knife.
This video explains how to remove and replace the rubber seal at the bottom of your garage door.
In this episode dave mars shows how to better insulate your garage door to help save energy and money.
Thread the t shaped edges into the weather seal track then slide the seal across the door.
When the door opens the rubber flexes so as not to be an impediment and when the door closes the rubber provides a strong air seal.
Door sweeps come in standard sizes but if you cannot find one.
Put enough temp nails in to hold the seal up against the jamb.
Clean the door bottom photo 2 then cut the new rubber seal to length with a razor knife.
Trim the soft weather stripping at the top of the side pieces at about a 45 degree angle so the top and side pieces overlap nicely.
Measure and cut the side pieces so they touch the header piece and extend to the garage floor.
Now temp nail the top seal to the jamb you want the inside edge of the pvc portion to be even with the inside edge of the jamb.
How to replace bottom weather seal on your garage door.