Sliding Door Track The Wood Below The Track On The Outdoor Side Of My Sliding Glass Door Is Rotting, How Do I Replace It?

The wood below the track on the outdoor side of my sliding glass door is rotting, how do I replace it? - sliding door track

Who left the sliding glass door installed in my house are exposed to bare wood beneath the track to the outside, it is occasionally or not at all to protect him. So I have to open the door and the track removed, then run the red timber. The hooks are not as lazy, looking down into the basement, so I hope this is only the visible part. Then I'll replace it with something better and put the door back together. "Can anyone suggest some tips?