On Sat, 20 Mar 2010 06:28:46 -0700 (PDT), KOS
wrote:

Hi, i just installed some crown molding in a room very long piece
25-35 feet. I had to cut it in two pieces.. The smaller piece where I
cut it is like 2 feet... But when I join it, (like a puzzle piece)
there is a pretty big gap there. Quite obvious, even when I paint it
it will show, what should I do???

I had to do a similar wall in my house. I used a scarf joint that
fits the long piece and the shorter piece. Make the short piece 1" or
so longer so you can sneak up on the perfect fit. Don't nail/glue
until you got the best fit possible. A well-made joint should become
nearly invisible.

Not quite as desirable, but ...
To fix a gap without removing the molding, fill the gap with Bondo,
shape, smooth and sand. Inspect with a work light, checking for any
flaws. Prime the joint. Inspect again. In addition to a visual
inspection, a slow brushing light touch can reveal irregularities.