One quite common misconception among non-practitioners, and also among some practitioners, is that matter can hinder the flow of Reiki. This is not correct.
Walls will not stop the flow of Reiki. If a dear one is having an operation and they won’t let you in the OR, you can surely and safely send them healing energy from wherever you are.
It doesn’t matter if you’re near or at the OR door, in the hospital cafeteria, in the park, or at home. You can just start sending using the distance symbol, and the flow will surely find your loved one.
People who’ve only taken Reiki together with massage sessions, or others who have not investigated or liken it to regular doctor’s visit, will often assume that you need to take off your clothes to receive treatment. This is not correct.
Just as Reiki can go through walls, surely it can go through the thin (or thick) clothes :).
This is a common belief among some practitioners as well, that things such as watches, necklaces, bracelets etc will interfere with the flow. However, just as Reiki can bypass walls, clothes, and even go all the way to the other side of the world, so can it go through the jewelry the patient or the practitioner is wearing.
However, if the practitioner finds it hard to concentrate in the presence of such objects, then it might be said that, indirectly, they hinder the flow, as they, by their simple presence, occupy the practitioner’s mind. If that’s the case, it’s best to simply remove them.