Rear brakes - Mondeo 2

It's the second time that the left rear brake of my Mondeo jams (sorry if my english is far for being perfect). I mean that it continuously
brakes and, of course, the wheel becomes warn. When I go to the garage, it takes less than one hour for them to repair this... Does anyone knows what do they do exactly. I think that it must be something very simple and I would like to do it myself in order to save time and money.
Thanks, JBK
PS: Mondeo 2 - 2003 - tdci - 65000km PPS: I bought it 18 months ago (26000km).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.