I reglazed about half the windows in the Hooker House (college apartment on Hooker Ave in Somerville) as a college student to help pay the rent. It looks like now I’ll get to do it again, but this time the homeowner I’ll be helping out will be myself. You may think that 1 1/2″ putty knife you use to spackle holes in your walls is made for that — it’s not; it’s made for applying putty to seal the glass into the window.
Fortunately, the window sashes themselves are in good shape, and this will also be a good opportunity to make sure the insulation and weatherstripping on each window is up to the task.