This view of a whittler’s backsprings shows the center liner that separates the two smaller blades at one end, and tapers down to nothing so both springs can apply tension to the master blade. It has become popular to use the modern (and misleading) term “Split Backspring Whittler” for this, but a better term would be “Tapered Liner” or “Tapered Divider” whittler. The reason why “Split Backspring Whittler” is a poor term for this is because a few early 19th century English whittlers actually used a single hand forged backspring that was split halfway up so as to operate all three blades. See: Split-Spring (Whittler)
Whittler, Tapered Divider (Tapered Divider Whittler)
