holes on the inside of metal fork blades, what are they I noticed there are two very small holes on both blades on my new fork. They are on the inner side of the blades at the end of the fork blade just above wheel axis mounting point. They are apparently designed to put there because they are at the same position and holes are smooth and no damage. So what the purpose of these holes? I noticed that my old fork also got similar holes, which I never noticed before.
On steel forks the tiny holes at the bottom end of the fork-blade are vent holes for the brazing process. The brazing produces fumes the fumes and the heat expands the air in the blade which makes that these holes are needed to evacuate both. On steel frames you may find similar holes in the seat-stays and in the chain-stays where they are usually close to rear drop-outs.
If you're worried about rusting because of moisture that could go inside spray some wax-coating or tar-based antirust inside, or a periodic jet of penetrating oil as I do.