The movie I'm trying to remember was probably made between 1971 and 1979. It ran in the late night time block, after the local late evening news on one of the 3 major US networks. It would fall into the spooky, supernatural drama category. It was in color. The one character in it I remember was a grandfather aged man. I thought it was Will Geer, but nothing in his filmography seems to fit. It was someone of that general type. Near the beginning of the story, the man is shown burying a knife, point up, in the ground. The knife has a series of rivets in the handle. Each rivet represents someone the knife has killed. At the end of the story, the villain falls on the knife and is killed.
The only other thing I can remember is that it was shot on videotape, I think. I'm not certain about that.
ETA: It isn't an episode of "Night Gallery", "Thriller" (1973) or "Journey to the Unknown.".
70's, late-night, on videotape....sounds like it might have been part of ABC WIDE WORLD MYSTERY.