When you are replacing your flax packing you will most likely never see this view unless you remove the transmission coupling and take the nut off. When removing the flax, with a pick, this is what you are trying to dig out! I took this photo to show the female nut with the old flax still in it. You can see the shiny surface where it meets the shaft and the thickness (3/16) of the flax its self.
This particular stuffing box is a 1 inch box from a 1985 Catalina 36 and uses three rings 3/16 flax packing. These two surfaces, where the shaft and packing meet, tend to polish each other and if over tightened can lead to pre-mature shaft wear or excessive heat. Over tightening of the flax nut, and running the stuffing box with no water drips, will eventually wear a grove in the prop shaft and ruin it. It's very important to allow a few drops of water per minute, when the shaft is spinning, for lubrication. Even the newer synthetic W.L. Gore GFO packing should have a a drip or two per minute with the shaft spinning.