This is the 12168th most frequent Russian word.
инвалиду
"Инвалиду" means "to a disabled person" in English.
In this sentence, 'инвалиду' is the dative form of the noun 'инвалид', used to refer to the person receiving the action of help.
Я помог инвалиду переправиться через дорогу.
I helped a disabled person cross the road.
Here, 'инвалиду' is in the dative case, indicating the person for whom the mechanism is suitable.
Механизм оказался пригодным для использования инвалиду.
The mechanism turned out to be suitable for use by a disabled person.
In this context, 'инвалиду' is dative, showing the beneficiary of the installation.