How to change a battery

Buy new Vivofit step tracker.
Use it until batteries run out.
Wait two years before buying new batteries.
Find screwdriver tiny enough to unscrew screws.
Ask Husband to remind you which way you have to turn it to undo.
Unscrew for ages before giving up and shaking the batteries out.
Fit new batteries.
Notice screen hasn't lit up but hope it will do when you tighten screws.
Tighten screws by turning in opposite direction from starting point.
Notice display still not lit up.
Shake vivofit.
Look on internet for instructions on changing batteries.
Undo screws.
Remove new new batteries.
Smear petroleum jelly over both sides using a made-do cotton bud.
Replace batteries.
Retighten screws.
Shake.
Squeeze.
Finish reading instructions. 
Replace Vivofit in strap.
Check display now.
Re-read instructions.
Remove Vivofit from strap.
Check location of little shiny thing (LST).
Replace Vivofit in strap with LST on the other side.
Press button.
Shake ferociously.
Read instructions more carefully.
Wonder if it needs to be connected.
Download app.
Get bored.
Throw Vivofit in bin.
Make cup of tea.
Retrieve Vivofit from bin and remove batteries. 
Store batteries in place so safe you'll never remember.