A via is an electrical connection between layers in a physical electronic circuit that goes through
the plane of one or more adjacent layers. How to test via hole,we have three soldring conditions.               

             1.granular solder                                          2.solder explosion                                   3.flat solder

when we meet these problems,we need to double dagger Such as W,WN,WW,also we could use
S and A according to hole size.

Plated-through holes, in this section there are eight on a multilayer board we could use probe to
test through cutting the gold line.

Normally we use many tip styles to test via holes,Such as W(sharp dagger),WN(dagger),WW(sharp dagger),

A(cone) .