Resin is mixed with a catalyst or hardener if working with epoxy, otherwise it will not cure (harden) for days/weeks. Next, the mould is wetted out with the mixture. The sheets of fibreglass are placed over the mould and rolled down into the mould using steel rollers (aka paddle rollers or consolidating rollers). The material must be securely attached to the mould, air must not be trapped in between the fibreglass and the mould.
Additional resin is applied and possibly additional sheets of fibreglass. Rollers are used to make sure the resin is between all the layers, the glass is wetted throughout the entire thickness of the laminate, and any air pockets are removed. The work must be done quickly enough to complete the job before the resin starts to cure. Various curing times can be achieved by altering the amount of catalyst employed. It is important to use the correct ratio of catalyst to resin to ensure the correct curing time. 1% catalyst is a slow cure, 2% is the recommended ratio, and 3% will give a fast cure. Adding more than 4% may result in the resin failing to cure at all. To finish the process, a weight is applied from the top to press out any excess resin and trapped air. Stops (like coins) are used to maintain the thickness which the weight could otherwise compress beyond the desired limit.