The fish is placed with the tail forward and the belly up or down in an alveolus. The opening of the fish can be ventral or dorsal, according to the needs.

To ensure that the fish is perfectly held for proper cutting, gutting and cleaning process, the tail has to be inserted in a hole provided for this purpose, between to retractable clamps.

The drag chain introduces the fish into the machine where it is processed in three stages:

1. First stage: The fish is cut it lengthwise. For this purpose, a rotating blade cuts the fish in half, in a perfectly symmetrical way, so that once opened it takes on a shape similar to a butterfly. The two symmetrical halves of the fish are joined together on the dorsal or ventral side according to the chosen fish infeed position. The central spine is always joined to one side of the open fish.
   The depth and length of the cut are adjusted and regulated according to the type of fish and the required presentation of the product.
2. Second stage: The gutting is carried out by means of a rotating brush that eliminates the viscera, leaving the fish perfectly clean.
3. Third stage:   The fish is washed with pressurized water so that when it leaves the machine it is perfectly clean and ready for consumption. Once the fish is clean, it continues to the exit, where it is released from the clamps that hold it, allowing it to fall to the next processing and packaging stage.
   Once the washing process is completed, the fish is moved to the exit of the machine where the clamps that hold the fish are opened and allow the fish to fall to the next stage of processing and packaging.