Full proof technique and full scape paper

We have been working hard to come out with a full proof technique to check the oil spill.
I was wondering what the usage full proof means. Why do many people use it this way instead of the correct foolproof? Probably there is an impression that people go for fully proof technique without really understanding the meaning.

A technique or technology or a machine can be foolproof and not full proof.
Fool proof is proof against human misuse or error or impervious to human incompetence.
Example: a foolproof detonator, a foolproof safety lock, a foolproof scheme.
This is just as in bullet proof vehicle which means the vehicle is proof against bullets.
We can also use this word as a verb.
Example: Foolproof this appliance.

Similar is the usage “Full scape paper”
I fail to understand the source of such a usage.
Many refer to writing paper which is a little longer than A4 sheet as full scape.
It is better if this is corrected as foolscap.
A foolscap paper is a full sheet of 13.5 in × 17 inches (342.9 mm × 431.8 mm).
The reason of such usage may be that this size is enough to make a clown’s (fool’s) cap.
Better we go with foolscap paper and foolproof techniques.