This is not always needed and could be considered a specialist skill but fitting a reverse tongue is always handy to know. To start, you will need a sheet of MDF that is approximately the same thickness as the groove on the edge of the flooring. Slot this piece of MDF into the groove of the wood and mark the overlap with a pencil.
Set your gauge on the saw then cut the board down the whole length. Repeat this process until you have enough MDF to complete your quantity. Then take the MDF and insert into the groove of your flooring and then fit your floor as normal.