I’ve experienced lots of trouble when I tried to open the battery cover of my new Sony Ericsson K800i. I read the manual and it said to slide the cover down using the thumb. I started using one thumb, two thumbs, the nails and it didn’t open. Before I ended scratching or damaging my lovely new gadget, I googled “open Sony Ericsson K800i battery cover” and to my surprise I found many forums where people were complaining about the same problem and asking for help, some of them ended up bringing the phone to a mobile phone store to ask the attendant to open it and they heard that their phones had a failure and probably would break if they proceeded with the attempt. Finally I read a comment from a guy who said: “A tip – try rubber gloves…” . Without hesitating I went to the kitchen got my “Dexter’s Mom” rubber gloves and guess what? The cover slid out with ease. As a matter of fact when I first touched the back part of my new phone I really liked the texture, it feels like rubber, but in the other hand, it didn’t take long for me to conclude that this nice texture doesn’t produce the necessary friction to hold the thumbs when I wanted to open the cover.
In my opinion, in spite of looking pretty good, Sony Ericsson have chosen the wrong material for the K800i battery cover because many consumers, who don’t have a clue about the rubber gloves solution, are damaging their phones when they try to open the battery compartment.

Pictures from Sony Ericsson Manual and Cartoon Network