In the movie Stargate, they have been trying to activate the Stargate for the last 2 years but could never get the right sequence. After Dr. Daniel Jackson figures out the seventh symbol, they try to activate it. When they get past the sixth symbol, Catherine Langford says to him
this is as far as we have ever been able to get
There are only like 30 symbols on there. How come after two years someone didn't say "hey guys, we already know the first six symbols, why not just loop through all 30 symbols until we find the seventh symbol"?