Hi

I discovered a section of rote on the lower corner of a window frame. The window is a small wooden slider type.

The section is about 2 inches in height and is evident both inside and outside.

Can I repair this section or do I need to replace the window?

My observatin about wood rot, is it's there, whether visible or not... I'd replace the window frame, because the rest has already started rotting anyway. Be sure to paint.

Press a small awl into the rot. If it is soft less than 1/2" in , you mau wish to use Minwax wood hardener Minwax® High Performance Wood Hardener - Wood Maintenance & Repair - Minwax.com. If it is deeper than that use Wood preservation, rot repair, and restoration using epoxy resin on boats and homes. . Though the best thing to do is replace the window sometimes that is not an option, or an option at this time. Rot can migrate and you don't want to have it affect the structural members of the house. These products can stop the process until you can do a proper repair.

I do agree with the answer by kidolph above! I have used those sort of products many times. However, I think that it would also help to know if fredjim is working with a window frame that is on a really old home (like maybe over 75 years old) or one that is more modern where you could actually find the dimensions of wood necessary to replace an entire frame.