Tralling can be found within the Experts section of the MQL5 marketplace, it was first uploaded on the 16th of November by its developer Dmitry Shutov, it has not received any updates since it was first uploaded and so the expert advisor is still on version 1.0.
Tralling was created for the MetaTrader 4 trading platform and was designed to automatically move the stop loss at a regulated distance from the current market price. It will work on any currency pair and will work on multiple pairs at once. The main input that is available is to choose the step required between each stop-loss movement.
The expert advisor will currently cost you $10 to purchase it outright, this will allow you to activate the expert advisor up to 5 times. Due to its low cost, there is no option to rent the indicator. A free demo version is provided, this may only be used on the strategy tester, there are no further details given regarding the free version on the site, it may still be worth downloading to try out.
Unfortunately, there are no user reviews given for Tralling so it is hard for us to gauge how users are finding it and whether or not it is doing what it is meant to do. There are a few comments, the developer of the expert advisor has not replied to the most recent ones and their last reply was back in 2016, so it is not clear as to whether he is still actively supporting the EA. We would suggest trying the free version and also contacting the creator with any queries that you may have just to make sure that it is still being supported before you make a purchase.