WHEN TO USE WASHERS DURING AN ENGINE BUILD

Hi Folks

So here I am working on a basket case 340, with 30 lbs of 50 year old Mopar engine related fasteners. I have been measuring hole depths etc to figure out the right bolts to use. Today, I was specifically measuring for timing chain/watepump/alt bracket bolts, and found that some of my fasteners have washers and some do not. This leads me to ask the question.............When do you use washers? And, the difference in application "flat vs lock". What say Ye? Thanks FABO.