Fifteen years ago, I visited Mark and Stacy in San Francisco and was introduced to apartment buildings with an air shaft.

Air shafts were built into apartment buildings to satisfy building requirements that demanded that densely built apartments had windows which opened into fresh air.

Mark and Stacy had one window which faced out into this ugly, uncleanable shaft. We went up onto the roof to get a look from above.

The photo above is from the top of the shaft, and should give you an idea of how much care was given to their upkeep.

I thought it was a shame that there wasn't a better view out of this precious window, but I had an idea! Could someone mount a mirror inside this shaft? At the right angle, a mirror could reflect the cloudy sky above into Mark's apartment. It would be a vast improvement, like a periscope for the entire window!

I never tried it.

The mirror idea sat in that vast repository of unexecuted plans for many years.

But I finally got my chance!

In Sacramento, my home has no airshaft, but it does have a window with a terrible view. My son's room looks out into a narrow side yard, with a view of a fence built close enough to count the fungal spores.

I told my son my idea of installing a large mirror outside, angled towards the sky, so at least he'd be able to see the sun and sky outside.

He said he'd rather have a view of the backyard.

I told him that would be no problem.

The plan was simple. Mount a half-sheet of plywood outside the window at a perfect 45° angle.

Next, cover the plywood with a giant mirror or with mirror tiles and adjust the angle to get the best view.

That's it!

On one hand, I didn't know what could go wrong. It was a really simple idea, but I had never seen it done before. There must be a million places where a view could be improved with a single mirror mounted outside.

I bought a 4' x 4' sheet of plywood and screwed a couple of temporary legs onto it. It fit the window pretty well. For the illusion to work well, the plywood would have to completely obscure the view from inside the house.

I should have started with a larger sheet of plywood. As the plywood tilted away from the window glass, it didn't quite obscure the entire view. The real fence was visible at the top, bottom and right side of the plywood.

I didn't think it would be a significant problem. I could add some additional plywood at the top and bottom edges of the sheet if needed.

I had a box of mirror tiles in the garage. Stacy's friend Ashley had peeled more than 100 mirror tiles off of her ceiling. She knew I loved mirror tiles after witnessing the Light Sharpener and donated them to me!

To help position the plywood, I mounted one mirror near the center.

On the first try, the mirror reflected a view of the stucco exterior, but with some minor adjustment it looked great! I could see right between the house and the fence, 15 yards to the back fence.

The window is in my son's room, but it is also positioned at the end of a hallway, so we could predict that it would be viewed most often from a particular angle. This was the perfect window for this mirror!

I added an extra row of mirrors to the right-side edge to extend the illusion.

Mirror tiles in place.

The adhesive dried in 90 minutes.

No it didn't.

A few days later, the adhesive was dry, and I was able to hoist the mirror board up into place. It must weigh 70 pounds, so I'm glad I didn't have to mount it 30 feet up in an apartment airshaft.

Even from outside, I was impressed with the illusion!

Here's how the 18 mirrors are positioned.

The backyard could look directly into my son's room!

The angle is important, but wasn't as hard to adjust as you might think.

And here is the result from inside the house! It totally works! Now I'm looking at the backyard!

I'll admit, it is a little gray in the winter, but there's 80% more sunlight coming in, and there's a clear shot at a cherry tree in bloom back there! The mirror window is incredible!

I'll need to paint the unfinished wood, and I'm sure the mirror will need periodic cleaning and care, but I think this is a cheap solution that people could use in all kinds of situations.

You better send me a picture if you try this!