Note: Opencart 3.X version of this extension can be found here: [OC-3.X] Out Of Stock Products At Bottom
Every store owner experience such things like OUT OF STOCK products and that is normal.
Most of the store owners do not thinks and disable these products that are out of stock at the moment.
So you as admin have 2 options:
1) Disable visibility of these products.
2) Leave these products together with other products on your website.
But lets take a closer look at both options:
The first one. If you simply disable products and will not show it, you lose Google ranking for them, which brings people into the shop so the more customer will come to your page and HIT page NOT FOUND the more you loose your page rankings in google and other search engines, Not to mention that this client wont even be able to read about your product. So you as admin lose on 2 things, Ranking and a customer that didn't spent a dime on your website.
Lets take a look at second option, that is leaving out of stock products listed together with other products. In this option you will not loose your rankings on google, but... if people will search on your website one or another product and get a list of too many products out of stock on the search results or front page, the sales also will drop. And he will think that your store is EMPTY.
But don't worry this extension offers you a THIRD option, the best one you can get from this situation:)
This extension will show OUT OF STOCK products always at the bottom list of any page (search results, categories,manufacturers, bestsellers, latest and etc). That is your customers always will be presented with Products that is IN STOCK and only at the very end of the list Out of stock ones.
So if people are coming in looking for a product no longer available, you have the opportunity to explain (product is discontinued by the manufacturer, etc) and recommend an alternative, either in the description or via related products.
This is a win win situation for both parties. You as admin will not loose Google rankings, and will not loose your new customer:) And for your client you will offer alternative product (maybe even better one):)
NOTE: LABELS (OUT OF STOCK) NOT INCLUDED
PS: if you have Journal theme, this mod has to be rebuilt in some parts due to journal custom controllers used when gathering product details from database (paid work) (it will not work out of the box with journal theme)