The right sign for "tunnel" depends on whether you mean the noun or
the verb. It also depends on what the tunnel looks like.
If you mean the verb:
* You can use a cupped hand doing a scooping movement to show a
backhoe or similar bucket-type device.
* You can use two cupped hands doing scooping/digging movements to
show an animal "tunneling"
* Use an index finger doing a forward corkscrew movement to show a
drill-type device tunneling,
* Use an index finger bending and unbending (1,X,1,X) as it moves
forward to show the tunneling of a worm (or similar creatures).
You can learn
American Sign Language (ASL) online at American Sign Language University ™
ASL resources by Lifeprint.com © Dr. William Vicars