How are you supposed to remove these screws?

[spanner48]

The blade was loose and I managed to remove one screw with time. It would seem neither screw has a serrated shank so both just turn in the hole.
I would prefer not to have to glue something onto the nut side as I think it will be difficult to clean the image up afterwards.
How were they supposed to be removed or tightened without serrations on the shank?

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Try using a long file [serrated face] alongside and covering the HEAD of the screw, and putting them into a vise, so that the nut is not covered. Clamp up tight. Then use a [split-nut] screwdriver to turn the nut out – whilst the file face holds the screw from turning.