The covered lineman executes a "rip-reach" technique. He takes an angle step at the playside shoulder of the defensive lineman and rips with his backside arm. His job is to turn the DLs shoulders and get him off-balance and prepared for his partner.
The uncovered lineman executes a "pull and overtake" technique. He takes a shallow pull step toward playside (sometimes called a bucket step) and works to take over the block of his partner.
The covered lineman wants to rip through his d-lineman to get to the linebacker, while his uncovered partner takes over his original block. If the covered lineman is unable to rip through because the DL fights to the outside, then the covered lineman stays with that block and the pull and overtake lineman pulls around that block and finds the linebacker.