I didn't see anyone link to a picture of a slide rule, so let me start with that. The British Thornton slide rule was the recommended weapon of choice at my school. I say weapon as the slide rule was a little over a foot in length and came in a nice, and study, plastic carrying case (I'll leave it as an exercise to the reader to imagine a classroom of 30 boys all armed with one of these).
Of course, it was also an intellectual weapon and a whole lot faster, if less accurate, than a book of log tables. To make sense of this, imagine a time somewhere between when dinosaurs walked the earth and pocket calculators were invented. At that time, you either had to do multiplication and division long hand or use your book of log tables or, if you didn't need more than 3 digits of precision, you could use your slide rule. If you take the time to look at the picture (and as already observed), you'll see that the numbers are etched into the plastic on a logarithmic scale thus turning multiplication into division into addition and subtraction which, in a slide rule simply meant moving the center slide! The slide rule description of how to use a slide rule is really good and needs no repetition by me. The only annoyance being that if you estimated incorrectly, your first attempt would slide the central piece in the wrong direction. Huh? How can that be? The point is that you have to decide whether a number should be represented between 1 and 10 or between 10 and 100! They're just the same, except for an order of magnitude.
As an indication of its sturdy case, my slide rule has survived multiple moves and currently sits on my desk at work among a collection of other toys. There's slight damage to the slide (the clear plastic piece with the fine line in it for lining up numbers - though I called it the cursor, not the slide) has some damage on one corner from either dropping it or being incautious when putting the rule back in its case. It hasn't affected the rule significantly but is annoying! Every once in a while someone will ask what it is and it is fun to watch their eyes widen as I explain how calculations were performed.
I use it occasionally but have become lazy and the act of reaching past the computer monitors, getting it out of its case, and then performing the calculation is typically slower than a little mental arithmetic or, imagine me hanging my head in shame, bring up the calculator app on my computer.
I hereby resolve that, when I get back to my office, the slide rule will come to the desk near me, and sit, outside its case, waiting for me to use it!