1
This isn't completely foolproof, but it works on most days.
2
No cooking technique is completely foolproof.
3
No system is completely foolproof.
4
A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
5
And, of course, no device is completely foolproof-the most important aspect of belaying with any device is paying close attention to your partner.