On Tuesday, June 28, 2016 at 6:16:00 PM UTC-7, Davoud wrote:
A neighbor is modifying the transom of a door to fit an opening. In the
process he broke the corner off the MDF bottom plate ...
Best glue to repair this break?

Many thanks!

As others have said, any old white glue. When it's dry, give the surface a pass with
a hot iron (use aluminum foil or teflon sheet to keep paint off the iron). The
glue doesn't make much of a seam bulge, but it goes down quicker with some heat
than with sandpaper.