Just checking in to say, "Hi!" and also offer my thanks for the information I found here about bringing an old Gillette "Fat Boy" F4 back to life. I've been using it for a bit and it started getting sticky trying to lock in a blade. Rather than soak the whole thing I used a GUM Blue (large) inter-tooth brush and some dish soap to clean out the buildup under the blade platform. Viola! It locks again. Thank you!