Garage Rotten Door Frame

[Hobbyman]

My prefab garage metal up and over door has a timber frame supporting
it.
Over some years the uprights at the bottom of either side have all but rotted away,leaving approx 4 inches of soft rotten wood at the base.How do I replace the rotten section.The garage door is permenantly closed,as the prefab has been coverted into a workshop.
Grateful for any advice.
Rgds Hobbyman

[greggy]

hi hobbyman, i would cut all the bad wood away and splice a new piece in with a matching bit. making sure you use a good quality wood glue. then prim, undercoat and then gloss it.