When the Vertical Stiles of Two cabinets Do NOT line up perfectly, most people simply use Two pieces of veneer to cover the combined stile, or put one piece of veneer over both stiles and simply let the 'lump' show.
Small items like this makethedifference between Professional results and anobvious "amateur"job.

Take an extra 5 minutes and do it Right!

In this Photo, There is a slight lump where the vertical stiles are screwed together.

We take ablock of wood and tap it with a hammeragainst the frames from the inside and outside of each cabinet to get them as even as we can.
Then wesand them even smoother. A belt sander works quickest, but a palm sander will also work. We use about 80 grit sandpaper.

Fill any remaining 'ridge' with "Bondo" brandauto body filler, available at any Wal-Mart.

Spread the Bondo with the flexible plastic spreader to "feather" the two vertical stiles. Spread it thinly. You won't need too much. Just enoughso that the ridge is no longer obvious. Wait a few minutes, then just as it begins to set ( it'll becomes No longer spreadable or workable), you can take a putty knife and scrape off any area that you put too much filler in. What you have left shouldalmost look like you want it to look after you give it the final sanding.

As soon as it become sandable (about 10 minutes),sand it smooth with electric sander (belt sander or palm sander: use 80 grit paper).Next, spray on or brush on some contact adhesive (3M super 90 , OR water based brush on type). Let it dry till dry to the touch. (see instructions on contact cement of your choice).

The water-based adhesive type is the ONLY one we will recommend, because of the flamable characteristics of the spray-on adhesives. The spray adhesives work extremely fast and are super strong, but must be used in a well ventilated area, so consider it NOT OUR RECOMMENDATION!

THEN, apply ONE SINGLE PIECE to cover both stiles.
Why have a extra seam when you don't need one?