> they found that none blocked the signal completely You can not block ths signal completeley. It is just the nature of radio wave that some small amplitude wi

> they found that none blocked the signal completely You can not block ths signal completeley. It is just the nature of radio wave that some small amplitude will get past the barrier, but you can lower the signal-amplitude so much, that the signal is worthless and a passive rfid chip will never respond. Alas, with a very strong sender, you might get through, but that is more a theoretical possibility or for the truly paranoid.