Nouns ending in -at are masculine.
The suffix often marks a status or condition.
Is contrat masculine or feminine?
lecontrat
The rule behind it
100% of -at nouns are masculine
In context
Ce contrat prend effet à partir de minuit.
This agreement becomes valid at midnight.
Cela faisait, pour ainsi dire, partie du contrat.
That was, as it were, part of the job.
Regarde bien le contrat avant de le signer.
Look over the contract well, before you sign it.