Ask MAKE is a weekly column where we answer reader questions, like yours. Write them in to mattm@makezine.comor drop us a line on Twitter. We can't wait to tackle your conundrums!

Barbara writes:

As a female who LOVES browsing the make.com materials, and who is courageous but sometimes missing some of the physics, I would love a basic (but thorough) explanation about the physics of trusses and how they distribute the load of the roof.

Great question! We were actually wondering this as well, so we turned to an expert to get some help. Here is what Dr. Drang (one of our readers) had to say in response:

Trusses, like all structures, are devices for transferring loads from where you don't want them to where you do. A roof truss takes the weight of the roof--and the snow on the roof if you live in that kind of climate--and transfers it out into the load-bearing walls of your house. A bridge truss takes the weight of the cars and trucks passing over it and transfers it to the piers. What makes a truss different from other structures--rafters, say, for a roof, or arches for a bridge--is the clever and efficient way it carries the load. Trusses tend to be very lightweight because they take advantage of geometry and the laws of statics. Let's look at each of these...

Ask MAKE is a weekly column where we answer reader questions, like yours. Write them in to mattm@makezine.comor drop us a line on Twitter. We can't wait to tackle your conundrums!

Barbara writes:

As a female who LOVES browsing the make.com materials, and who is courageous but sometimes missing some of the physics, I would love a basic (but thorough) explanation about the physics of trusses and how they distribute the load of the roof.

Great question! We were actually wondering this as well, so we turned to an expert to get some help. Here is what Dr. Drang (one of our readers) had to say in response:

Trusses, like all structures, are devices for transferring loads from where you don't want them to where you do. A roof truss takes the weight of the roof--and the snow on the roof if you live in that kind of climate--and transfers it out into the load-bearing walls of your house. A bridge truss takes the weight of the cars and trucks passing over it and transfers it to the piers. What makes a truss different from other structures--rafters, say, for a roof, or arches for a bridge--is the clever and efficient way it carries the load. Trusses tend to be very lightweight because they take advantage of geometry and the laws of statics. Let's look at each of these...

Ask MAKE is a weekly column where we answer reader questions, like yours. Write them in to mattm@makezine.comor drop us a line on Twitter. We can't wait to tackle your conundrums!

Maurice writes:

I'm trying to understand antennas. I mean, really understand them. But I need a book that's gonna spoon-feed me all my antenna wisdom. Any recommendations?

My knowledge of radios end just before antennas (literally, I used to help design power amplifiers for them!), so I asked a few of my colleagues for recommendations.

Diana Eng, fashion whiz and ham radio enthusiast, suggests the ARRL Antenna Book:

She pointed out that it about 1000 pages, and if you can get through the whole thing you will probably be somewhat of an antenna expert! Diana also produced a video about directional antennas that might be of interest to you.

Next, I talked to Matt Stultz, who runs ham radio classes at Hack Pittsburgh. He also recommends the ARRL Antenna Book, but suggested that for a beginner, the basic antennas book might be a better place to start:

Between those two books, you should have more then enough material to get a start in antenna design. Good luck!

Know of any other great books on antenna design? Let us know in the comments!

Ask MAKE is a weekly column where we answer reader questions, like yours. Write them in to mattm@makezine.comor drop us a line on Twitter. We can't wait to tackle your conundrums!

Liz writes:

I'd like to install an outdoor wired (or wireless) low light stationary camera outside my residence - I'd like it to annunciate to a mirror sort of similar to the rear view mirror camera that only activates once the vehicle is in reverse. Is there a way to develop a mirror capable of switching to the camera on cue by using a light switch or something along those lines? The "mirror" would be located adjacent to my front door and framed aesthetically as it's primary role would essentially be a mirror until you needed to access the camera. Thank you in advance for giving us a heads up!

Oh, that sounds like a fun project! You can't really buy a mirror that can be turned on or off (at least to my knowledge). Instead, what you want is a 'one-way' or half-silvered mirror. These are the kind of mirror that you might see featured in a movie about an interrogation room, where observers can hide in an an adjacent room and look through.

The mirror doesn't really only allow light to pass in one direction, though. Instead, it has a fine metal coating on it that reflects one half of the light that goes through it, and lets the other half pass through as if it were a regular pane of glass. The trick is that the secret observation room is kept much darker than the investigation room, so that any light that does make it the wrong way through the mirror is overpowered by the reflection from the main room. If the observers mistakenly turned on their lights (or lit a cigarette), the people in the investigation room would be able to see them!

If you build a little cabinet to hide the display for your camera, and put a piece of one-way mirror glass over the front, then I think you will get the effect that you want. To be able to see the feed from the camera, just turn on the display, and it will instantly visible. Look for TV mirror glass- it's a product designed to do exactly what you are looking for. I was able to find a few manufacturers that are selling small sample sizes for ~$20, which should be more than adequate for a small camera monitor. Good luck with your project!