As Chrispy has just said, spool tumblers look like a spool, hence the name.
A tumbler is a pin that stops the keyway from turning and in
doing so, keeps the lock locked.
A spool pin/spool tumbler:
http://www.crypto.com/photos/misc/lockp ... pool1.html
Another spool pin:
http://www.crypto.com/photos/misc/lockp ... pool2.html
Here is one in action:
http://deviating.net/lockpicking/02.05- ... nding.html
A spool will try to force the plug to go in the opposite direction that
you are trying to turn the plug.
They are there to make you think that a pin is set correctly, when in
fact it is not.
They are used to hinder picking. These usually pose a problem to those
new to picking and are found in a lot of really cheap locks as well
as better brands.
(The first link to a spool picture, is out of an Abus lock... decent quality)
There is a lot of info about spools on this site.
Just use the search button before you post.
