"ultimate" fingers-crossing
Refers to where you also manually cross your ring-finger over-top of "Big Boy", and then cross "Little Boy" over-top of your ring-finger; the theory is that perhaps this will give you a better chance of not getting your a** blown off than you'd have from crossing just your first two fingers. Extra points if you cross all four fingers of both your hands in this way, and/or if you also scuttle around and similarly-arrange da hand-appendages of any and all bystanders (provided their fingers are slender and limber enough to fairly-comfortably do so, of course) prior to saying, "Well --- here goes nuttin'"... with THAT voluminous number of "overlapped digits", it would conceivably put pressure on Fate to allow your endeavor to succeed, similar to how a prayer-chain supposedly does with God.
My elderly neighbor had given me a ride downtown to fill my water-jogs at the local public faucet, and he was concerned that his car's severely-worn starter wasn't going to "mesh in" correctly when he turned the key. So I jokingly showed him the "ultimate" fingers-crossing when he was ready to try starting his car; he looked at my seemingly-impossibly-"pretzeled" fingers and said a bit sadly, "Zheeesh --- I could NEVER do that with my poor old craggy arthritic fingers!", and then tentatively "twisted da brass" and beamed appreciatively when the car's engine whirled right over! "I guess crossing your fingers like that DID work," my friend chuckled.