This happens where I work- one of my coworkers is here Monday - Thursday (10 hour days) but takes Friday off. He's the only one with knowledge of a lot of our l

This happens where I work- one of my coworkers is here Monday - Thursday (10 hour days) but takes Friday off. He's the only one with knowledge of a lot of our legacy systems, so a lot of potential work doesn't happen on Fridays. I'd argue that more of us should learn what he knows to avoid "hit by a bus syndrome" but we don't have enough spare man hours to devote to that.