Most options are self-explanatory but some of them should be explained a bit more

You can use external trade script (ETS).

First of all, ETS should somehow count incoming hits. Usually it's done by including something like <? include('/path_to_another_script/in.php') ?> into your templates.

Then each click has to go through SCJ out.php so SCJ can count clicks at thumbs, and the scj_out.php redirects to ETS_out.php and ETS_out.php decides where to send a click: gallery or trade. You have to specify ETS out.php in Rotation - Settings - Alt Out like /url__to_ETS/ETS_out.php?url={URL}

So usually it looks like this:

/scj/out.php?url=http://gallery.html → SCJ counts clicks at thumbs and redirects to /url_to_ETS/ETS_out.php?url=http://gallery.html

As you can notice {URL} is being replaced by an actual gallery URL.

Alt out and custom galleries

Let's say we have an URL like http://domain/gallery/gallery_slug/index.html and this is a custom gallery. W\o rewrites it looks like scj/out.php?url=content&slug=gallery_slug - so if SCJ decides to send to a trader - it redirects right away. Otherwise it can load 'gallery_slug' from DB and show a gallery.

When we use ETS and user clicks at http://domain/gallery/gallery_slug/index.html this click is being sent to scj/out.php?url=content&slug=gallery_slug, SCJ counts hits and redirects to /url_to_ETS/ETS_out.php?url=http://domain/gallery/gallery_slug/index.html and let's say ETS_out.php decides to send to a gallery (http://domain/gallery/gallery_slug/index.html). As you can see at this point we ran into an infinite redirect.

So what to do

By default you use alt out we add &ao to gallery's URL and SCJ redirects to ETS_out.php?url=http://domain/gallery/gallery_slug/index.html?ao

In this case when ETS_out.php redirects back to SCJ we know that we have to show a gallery, not redirect to ETS_out.php