David,
- Turn on the gumball.
- Hold down shift and command and click the surface you want to bring flush and the two radius surfaces at its ends.
- If the you know the distance you want to move to make it flush use the arrow on the gumball.
- Alternatively use the move command and line up the midpoint of the “bring flush” surface with the midpoint of the red surface.
Should look like the picture below with the correct surfaces selected.
Luck,
Also David