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[ The PC Guide | Systems and Components Reference Guide | Keyboards | Keyboard Construction and Operation | Keycaps ]

Keycap Attachment and Special Keycaps

On most keyboards, the regular keys are attached to the keyswitches simply using friction: you press the keycap down on the keyswitch, and a plastic piece in the top of the keyswitch (often shaped like a plus sign; "+") fits into a matching slot in the underside of the keycap. To remove the keycap, you just hook something under the bottom of the keycap and apply gentle but firm pressure until it pops off. This is fairly straight-forward, and is of course the whole point of keycaps, that they should be easy to remove and replace. (You do need to be careful not to apply excessive force, or you could break the keyswitch or the keycap.)

This simple attachment method works for the regular-sized keys, but does not work for special keycaps, such as those used for <Shift>, <Enter>, and the <Space Bar> (and in some keyboards, other keys such as <Backspace> or <Tab>). The problem is that these keys are too large to attach the way regular keys do. If they just snap these keys into the keyswitch in the center, the key will work, but only if you press right in the middle of the key. If you attach these large keys in the conventional way, and hit the edge of one, the central attachment point would act as a fulcrum of sorts, and the keycap would get stuck. Even if the keycap went down, the motion would not be smooth and your typing would be interrupted.

Of course, the whole point of enlarging commonly-used keys like the <Space Bar>, <Enter> key and so forth is that they should be easier to use. So these keycaps add to the regular keyswitch attachment point a "C-shaped" metal bar that runs the length of the key. The ends of the bar attach to the underside of the keycap, and the bar fits under small tabs built into the base of the keyboard. The bar serves to even out the pressure placed on the surface of the keycap, so that you can press anywhere on the key and have the key work smoothly. Some very large <Enter> keys that are both as wide and as deep as two regular keys, actually have two bars, arranged perpendicularly. This "two-dimensional" design spans the entire width and depth of these large keys so they operate properly.

The <Enter> key from one of my keyboards, placed face down
to show the pair of "C-shaped" metal bars that are used to allow
the key to be pressed down smoothly. (The screw is just to
hold the bars up so you can see them properly. And no, it was
not fun to put this keycap back in, but I was able to do it. :^) )

You should be warned that removing a keycap that uses a metal bar can be difficult to do; and replacing one will be difficult to do. :^) The problem is that you have to get the bar to catch the tabs on the keyboard base, but the keycap itself blocks your light, and your fingers. Not a fun task, as I know from personal experience. :^) So I'd advise you not to remove these keys unless you must. If you do, be very slow and careful in doing so, as if you break the plastic tabs that hold the metal bars in place, you may ruin the entire keyboard--and they are quite fragile. (And you'd be surprised how hard a keyboard is to use with a sticky <Enter> or <Shift> key...)

Next: Keyswitches

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