It is recommended that a Bonder be applied prior to the application of all One Component Resins.  A filler is added to these resins to achieve a higher (thicker) viscosity.  When applying One Component Resin to build the artificial nail there will be places on the nail plate that will be in direct contact to the filler and not the gel resin, therefore there wouldn't be proper adhesion in these areas.  Using a bonding agent first will prevent any lifting issues from the filler.