If you describe a guarantee or plan as ironclad, you are emphasizing that it has been carefully put together, and that you think it is absolutely certain to work or be successful.
[emphasis]
...ironclad guarantees of safe passage.
The case for testing now is ironclad.
ironclad in British English
adjective (ˌaɪənˈklæd)
1.
covered or protected with iron
an ironclad warship
2.
inflexible; rigid
an ironclad rule
3.
not able to be assailed or contradicted
an ironclad argument
noun (ˈaɪənˌklæd)
4.
a large wooden 19th-century warship with armoured plating
ironclad in American English
(ˈaɪərnˌklæd)
adjective
1.
covered or protected with iron
2.
difficult to change or break
an ironclad lease
noun
3.
a warship of the 19th cent. armored with thick iron plates
Examples of 'ironclad' in a sentence
ironclad
`That your father is now the one person with an ironclad alibi for the time of Joanne Short's death.
Telushkin, Josef THE UNORTHODOX MURDER OF RABBI MOSS (2001)
His conqueror's mask, all hard planes and ironclad determination, warned her she would win no concessions on that front.