Estes Interceptor Build #1250, Part 5, Fin Gluing and Shaping

The instructions say to round the leading edges and taper the trailing edges.
I can't see any reason to taper the trailing edges. This heavy model won't gain any extra altitude by airfoiling the wings.
I'll round the leading and trailing edges.

Before gluing the upper and wing fin parts together, round some of the fin edges. Note I wrote "some" of the edges.

Look close at the picture, I've marked the edges that will be rounded now. The leading edges of the larger two piece fins will be rounded after the the dorsal (front) fin pieces are glued on.

After the glue dries, round the leading edges of the larger fin sides.

Hold your block at a 45 degree angle and sand into the corner.
Afterwards, use a small tightly rolled piece of 400 grit to clean up the inside corner joint.