Instructions:

Articulator: tip of the tongue
Point of Articulation: alveolar ridge
Manner of Articulation: Flap – The articulator strikes its point of contact directly, as a very brief stop.
Voice: voiced – Vocal folds are close and vibrating.

Occurrence:
Afrikaans (Standard), Albanian, Arabic (Egyptian, Levantine, Moroccan), Armenian (Eastern), Asturian, Assyrian Neo-Aramaic, Austro-Bavarian, Basque, Catalan, Chechen, Danish, Dutch (Many dialects), English (Received Pronunciation, Cockney, Australian, New Zealand, Dublin, North America, Ulster, West Country, Irish, Scottish, Older Received Pronunciation, Scouse, South African), French (African French, Corsica, Rural Acadian, Rural France, Rural Quebec, Southern France), Galician, German (Northern, Standard, Southern), Greek, Hebrew (Mizrahi, Sephardic), Ilokano, Irish, Japanese, Korean, Maori, Mutsun, Norwegian, Persian, Polish, Portuguese, Punjabi, Sicilian, Slovene, Spanish, Tagalog, Turkish, Zapotec (Tilquiapan).
(Source: https://en.wikipedia.org/wiki/Alveolar_flap#Alveolar)