If you have an old house, you may have a door with a mail slot. Is this something that did not exist years ago or am I correct in assuming that this was installed by someone who lived here previously? Can you put a mail slot in a glass door? I have just moved into my new home and noticed that there is a small metal flap with a small latch on my front door, which appears to be for the postman to drop off post through it. Any tips would be appreciated! Can you put a mail slot in a glass door? I don’t want to keep it but can’t seem to figure out how to take it off. The previous owner had a mail slot placed on the bottom of the glass. I just bought this house and there is an old sliding glass door. When you think of security doors, do you think expensive, can you put a mail slot in a glass door, remove mail slot from door? Cost shouldn’t be your main concern when it comes to securing what matters most to you. When you invest in one of our massive steel doors for sale, you can rest assured knowing you’re purchasing a heavy duty doorman to protect what matters most – your valuables, or items that mean the world to you… And when it comes to security here at USA Security Products, quality isn’t just a buzzword: it’s our mantra. Whilst each gun safe door is a thing of beauty, it’s the security features that set them apart from the competition.