Horiz. Clapboard Repair: Cutting Out Of A Small Section: How ?

Hello,

Can't quite envision a "clean" way of doing this:

Let's say you have to replace a foot long section right in the middle of perhaps a 12 foot section of horizontal clapboards.

How does one cut it out; only the foot long section ? (leaving the rest, on either side, in place).

The only way I can think of is to use a keyhole saw, as that would enable me to place the teeth flat right against the wood. But, how does one cut the section that is underneath the clapboard above ?

This seems like one of those subjects where there is a real trick involved, but I don't see it.

Any how-to suggestions would be appreciated.

Thanks, Bob