The single most useful tool I used to carry when blagging it in various builder trades. There are just so many situations where a really sharp blade comes in handy.
This particular model has a simple but sturdy locking wheel that I find much more practical than the usual stepped version. You soon learn to operate it one handed, and for a quick slash of some packing you don’t even need to lock it before you retract it and slip it back in your tool pocket. To extend a short steady blade, or the full length is equally quick. The “carpet tucker”, as Olfa calls it, at the rear end is also surprisingly useful when you always have it handy. Opening a can of paint, forcing some casing apart, lifting staples, scratching away some dry glue drippings, or as a screwdriver in a pinch.
I guess there is a reason why I almost never see a painter carry anything else other than this particular model.