Finally someone gives a clear answer to the op's question.
The following is for the home DIY type boards that at most are double sided. I expect there are very few 4 layer homebrew boards in normal use. DJ, was it you that did some 4 layers?
While a via can be used to get across a trace on the same layer, a "via" is simply a hole thru the board from top side to bottom side and is used with double sided boards. (home use)
As said before, a short piece of wire cab be used to connect the two sides (layers). Even better is a rivet to connect the two layers. Since getting smoe rivets - I LOVE those for connecting vias.
Using vias to keep track of jumpers on the top layer is a good idea - I'll try to remember that trick.
Great group of folks here and I've learned a LOT.
Ken H>
--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> A via is a hole in the PCB that lets you connect copper on different
> layers. While they're physically the same as the holes for component
> leads, PCB keeps them separate so that you can do things like "select
> all vias" or "increase all pin sizes by 5 mil".
>
> Note that PCB automatically adds vias if you're drawing a trace (line
> tool) and select a different layer (number keys).
>