Mounting handlebar without scratching it

to free up a spare hand from the screwdriver method above try this.

1. Remove the bolt from the bar clamp of your stem
   
2. Insert a 1p coin into the slot in the clamp ensuring it does not overlap with where the bars will go
   
3. inset the bolt from the other (threaded side) and tighten against the 1p coin gently. This should open the clamp up and keep it open for you to slide through the bars. Be careful not to open the clamp up too much or you can damage it.
   
4. Once the bars are in remove the bolt and 1p and the insert the bolt into the clamp the normal side and tighten away to your hearts content.
   
   

This method does not work for all stems as you need to be able to access both sides for the bar clamp. Those it does work for though, it has the advantage of not scratching any paintwork or even worse denting the stem as twisting screwdrivers has been known to do.

Hope it works for you