It is a wooden drum made of animal skin tensioned or loosened through ropes placed alongside the body of the instrument.

Their construction is similar to 19th-century American and European military or field drums, and Latin American wooden bass drums.

Traditionally strapped over the shoulder, alfaias are played with a distinctive technique in which players hold the weak-hand drum stick inverted to get the proper attack on the head.

Alfaias are also known as "Rope-surdos" or "Maracatu-drums", and the largest ones are called "Alfaias-marcantes".

The alfaia has a characteristic deep, heavy sound, different from other bass drums such as the surdo or kick-drum, and they are used mainly in the Northeastern folk rhythms and dances of Brazil, such as maracatu, ciranda and coco-de-roda.