A hybrid drill bit comprising: a body having a plurality of blades , each blade comprising a plurality of earth formation cutting elements , the body further comprising a plurality of mechanical fastener receptacles ; at least one rolling cutter assembly pocket formed into the body and comprising a first torque-reacting structure, wherein the pocket is disposed between adjacent blades ; at least one rolling cutter assembly comprising a head onto which a cutter element is rotatably coupled; the head comprising a second torque-reacting structure configured to operatively engage the first torque reacting structure, and a plurality of mechanical fastener openings , wherein the plurality of mechanical fastener receptacles of the body correspond with the plurality of mechanical fastener openings of the head; a plurality of mechanical fasteners configured to securely and removably couple the at least one rolling cutter assembly to the pocket; the hybrid drill bit characterised in that it further comprises: a locking structure formed on a portion of at least one fastener and configured to provide an interference fit between the locking structure and an associated fastener opening in the head ; a plurality of locking caps each configured to engage an exposed portion of a fastener and prevent relative rotation between the fastener and the cap ; and a plurality of weldments engaging at least a portion of each locking cap and configured to prevent dislodgment of the caps from the fastener and to prevent relative rotation between the cap and the body . a body having a plurality of blades , each blade comprising a plurality of earth formation cutting elements , the body further comprising a plurality of mechanical fastener receptacles ; at least one rolling cutter assembly pocket formed into the body and comprising a first torque-reacting structure, wherein the pocket is disposed between adjacent blades ; at least one rolling cutter assembly comprising a head onto which a cutter element is rotatably coupled; the head comprising a second torque-reacting structure configured to operatively engage the first torque reacting structure, and a plurality of mechanical fastener openings , wherein the plurality of mechanical fastener receptacles of the body correspond with the plurality of mechanical fastener openings of the head; a plurality of mechanical fasteners configured to securely and removably couple the at least one rolling cutter assembly to the pocket; the hybrid drill bit characterised in that it further comprises: a locking structure formed on a portion of at least one fastener and configured to provide an interference fit between the locking structure and an associated fastener opening in the head ; a plurality of locking caps each configured to engage an exposed portion of a fastener and prevent relative rotation between the fastener and the cap ; and a plurality of weldments engaging at least a portion of each locking cap and configured to prevent dislodgment of the caps from the fastener and to prevent relative rotation between the cap and the body . a locking structure formed on a portion of at least one fastener and configured to provide an interference fit between the locking structure and an associated fastener opening in the head ; a plurality of locking caps each configured to engage an exposed portion of a fastener and prevent relative rotation between the fastener and the cap ; and a plurality of weldments engaging at least a portion of each locking cap and configured to prevent dislodgment of the caps from the fastener and to prevent relative rotation between the cap and the body . <EOS>