I had just snapped a chalkline across the face of some very expensive western red cedar paneling when I realized I had measured incorrectly. To lift the chalk out of the very porous veneer without smearing or rubbing it in, I mixed up a glob of stiff flour-and-water dough and just dabbed at the chalk. Followed up with light sanding, this made the goof virtually disappear.
James Bolker, Lyle, WA