A locking mechanism for locking a rod in a screw and rod fixation assembly includes a cap having a sidewall and a locking element extending from at least a portion of the sidewall. Locking mechanism cooperates with a receiver component for a spinal fixation rod to lock the rod in the receiver without requiring application of torque. A method of locking a spinal fixation member in a receiver of a screw fixation assembly includes the steps of placing the spinal fixation member into a channel of a receiver, axially advancing a locking cap into the receiver toward the spinal fixation member without application of any torque, and securing the locking cap in a locked position above the spinal fixation member without application of any torque.