Sinew backing was attached to a bow using a marlinspike and a pair of cable twisters. One end of the marlinspike is tapered, and is used to raise strands of sinew when lashing them to the stave, and for tucking in the ends of the lashings. Cable twisters are turned outwards in opposite directions at each end. They are used in pairs for twisting strands of braided sinew into cables that run along the centre part of the bow stave.
"The back (of the bow) is reinforced with a cord of reindeer sinew, which they tighten at will by means of little marlin-spikes (kréputark) always hanging from the quivers. (Émile Petitot, quoted in Savoie, 1971: 155)