How can one remove this chainring? I have a crank and chainring setup pictured below, running as a 1x with a chain guard where the outer ring would be.

I am trying to remove the chainring from the crank and am having trouble.

The bolts take a standard allen key but on the other side there is an irregular screw that needs to be held in place in order for the bolt to loosen. It seems one would need a special tool to hold it in place while he bolt is loosened.  

I managed to loosen one of the bolts without holding this screw in place, but the others won't budge, i.e. they turn with the bolt and thus do not loosen.  One can see in the pictures below that there isn't enough clearance to fit a standard flat head screw driver to hold it in place.

Is there a common tool(s) I can use to remove these bolts?  If not, what is the tool called that I need in order to loosen these bolts?



(below) Not enough clearance to use a standard flat head



(below) A bolt that did loosen, without any holding in place
What you need is known as a "Chain ring spanner" or a "Chain ring peg spanner". Very cheap to purchase.