The can probably is OK because opening it does not materially change the thing. If it had an attached cover that you had to tear off, would be different busines

The can probably is OK because opening it does not materially change the thing. If it had an attached cover that you had to tear off, would be different business. Padlocks I'd say look ok but then for an observant Jew there wouldn't be too many regular Shabbat activities that require dealing with padlocks. Doors are certainly ok, I've seen observant Jews opening (and closing) doors on Shabbat many times. Of course, if a particular door has e.g. an electronic sensor there might be complications... But again, as an observant Jew you probably wouldn't find yourself in a place with such doors on Shabbat. But the proper way to address this question is to ask your rabbi of course. If you're an observant Jew, you have one. If he says it's OK then it's OK, if he says it's not then it's not. Sometimes they disagree, and sometimes the disagreement grows big so some strict people for example only eat food that has the Kosher stamp of a specific authority and not the others, and so on.