Which side is the tongue, which the groove, and which goes first during installation?The tongue is the side that you will want to place against the wall as you start your laminate-flooring installation. If you mix the two up and start with the groove side, you will have difficulty completing the installation because you will essentially be installing the flooring backwards.In the line drawing above of an Express Clic System plank profile, note the orientation for the tongue and the groove. As this illustration indicates, the tongue for any Swiss Krono click system (Express Clic and Drop-and-Lock, Clic2Clic and Tap-and-Lock, 5G and Angle-to-Angle) protrudes outward, while the groove part forms a cavity for the tongue of the next plank to fit into. Both are cut to micron precision so that they create a snug, interlocking installation.You will want to start in the left side of the wall you pick with the tongue on the long side of a plank facing the wall. The tongue against the wall should be removed. You can use a sharp utility knife for the 7-mm or 8-mm product, but 10-mm or 12-mm product will require a saw.It is important to work from left to right to avoid damaging the tongues on the short side of the boards.Before getting started with your installation project, and after you have acclimated your laminate flooring planks, it’s a good idea to get all of your planks oriented in the same direction with the tongue side of each plank parallel to the wall you will be installing against.