"JB MacDonald" wrote in message
. ..
I know how to find the center of a pipe, using a vee block, but my question
is how do you scribe a line from one end to the other , so the first hole
is in perfect alignment with the last hole .. take for example a 20 foot
pipe , or tubing . If we had a 20 foot layout table fine , clamp pipe down
and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Use a Loooong v block, a piece of angle or channel iron/aluminum.