бе́з толку

adverb

1.
uselessly, in vain, for nothing, to no effect
Мы без толку прожда́ли его весь день.
We waited for him all day for nothing.
Says that the action brought no result.
2.
senselessly, pointlessly, aimlessly
Он без толку бе́гал по ко́мнате.
He was running around the room pointlessly.
Says that the action lacks sense or direction.

Examples

Я попроси́л студе́нта успоко́иться. Э́то бы́ло без толку, всё равно что со сте́нкой разгова́ривать.
I asked the student to quiet down. It was like talking to a wall, nothing happened.
Мы весь день прокопались в саду без толку.
We spent the whole day messing about in the garden to no avail.
Ждать без толку.
There's no point in waiting.
Морочащийся с починкой мастер весь вечер провозился без толку.
The repairman, struggling with the repair, spent the whole evening on it to no avail.