REASONING

Find the CAPS LOCK key, and press it once.

Better yet, find the power button, and press it once ...

Good idea, Krekel . . . he or she will need to press and hold that power button until our pain goes away . . .

Well, tapping it will do as well, but (s)he'll has to use a sledge hammer.

PS; is this correct?

'he will has to use'

No, doesn't sound right. Is it 'he will have to use ...'?

Yes, it is "he will have to use". In English, the will/shall form of the simple future tense of any verb including "to have" can be formed by will/shall + the infinitive (with "to" removed). So the future of (to) have is

I will have
he/she will have
you will have
they will have
you will have
they will have