When you process wood in your shop, it is helpful to make notations on boards so you remember which have been cut to length or run through equipment like planers or jointers. Instead of using pencils for the notes, use chalk. Chalk lets you mark the wood without marring it so you can be more liberal with your notations. An inexpensive children's sidewalk chalk set will provide several colors so that you can color-code your marking system.
Buy a pane of glass that is 1/16 in (1.55mm) smaller that the window opening on all sides. Chip out any old putty. Clean out the recess, and paint it with primer. Lay a bed of fresh putty in the rabbet in the window frame. Press the new piece of glass into position around the edges – not in the center, where it could break. Insert glazing brads or clips to keep the pane of glass in place.