One aspect of the Linchpin (as defined by Seth Godin) is their ability to solve extremely complex problems. If there is a problem that has everyone stumped you can elevate it to the Linchpin and have faith that they will come back with an answer. You can count on it.
Another worker type attempts indispensability by making a system so unnecessarily complicated that they are the only one who can decipher it and use it.
The problem with the latter is that they clog up productivity and motivate others to work around them.
Thomas Duggan 