Abstract: A valve or tap for fluids comprises a body, a revolving shutter in the body between a closing position and opening position, and control mechanism for rotating the shutter. The control mechanism can be moved axially between a raised position in which it is locked angularly to the body of the valve and a lowered position in which it is free to rotate. The control mechanism may be normally held in a raised position by an elastic part. The control mechanism may include a first pin joined to the shutter and a second pin constrained in an angular direction to the first pin. The second pin may be movable in an axial direction in relation to the first pin between a raised position for locking to the body and a lowered position for unlocking from the body.