Those are bleeders for the wheel cylinders. They colud be sprayed with penetrant and maybe put a little grease around the threads to help then come loose after letting them soak.
NOTE: do not open the bleeder unless you are ready to bleed the brakes or are going to do repairs to the brake hydraulic system.


There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!