How to identify lanes on large agarose gels?

[Peter Frank]

Hi,

I ran a large agarose gels for analyzing PCR products. The gel has
many narrow lanes. Problem is that there isn't a band in every lane,
sometimes there are several empty lanes between bands, and this makes
it difficult to identify the lanes because the wells are not visible
on the gel picture. However, I need to be able to clearly identify the
lanes so that I know where there is a PCR product and where there is
none.

Drawing equally sized lines to locate the lanes did not really work
well because of the imperfection of the gel or gel run.

Can you give me any tips on how to handle this problem? I was thinking
of putting a marker lane onto the gel every 4 lanes so that there
wouldn't be large spaces without anything. But I am not sure if this
is the best solution (besides, it would cost me a lot of DNA marker).

Peter