End plates are at the top of every single wall in the home. The problem with end plates is there's generally a quarter inch to an inch gap left during construction of the home. This allows for air leakage which lets the cool air escape the home in the summer and warm air to escape in the winter.
When the hot air leaks into your attic in the winter, ice dams occur on your roof. Ice dams can cause thousands of dollars of damage to your home!
Air sealing end plates is the first, and most important, of multiple treatments to eliminate ice damming.