Thin, flexy stick (Yardstick'll do, but thinner would be better). Secure at
each end (clamps, couple of nails, whatever) pull down to a known depth,
whatever suits your fancy. (e.g. 8" for a 4' span) Mark with marking tool
of your choice. Cut with jigsaw or other favorite motorized or non
motorized cutting tool.
Don't forget to cut your stick a decent percentage longer than the span
you'll be marking.
I've seen it done using a small diameter piece of PVC pipe. Put nails at
the high point of your scallop, and one at the low point, trace the line,
and cut to match. Alternately, draw a template of a scallop you like on a
thin piece of something (luan plywood would be a decent choice), then tack
it to the fence, trace the line, and cut on the line. Surprisingly, I've
seen the cut made with a small circular saw, more or less forcing the blade
around the curve. I'm sure a jigsaw would be a bit slower, but it would be
less of a brute force approach.
I bought a Dewalt barrel type jig saw and can attest to its aggressive
cutting ability. Since, I've move to a similar SEARS model (the cast foot on
the Dewalt cracked!) and find it does as good a job. Years ago I cut some pt
fence slats to make a pineapple design in the voids. I used a little saber
saw to cut some forty pattern cuts and I can attest to the "world of
difference" between it and the $169 De Walt.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.