The Stanley "Bed Rock" plane has a similar but less convenient device.
[Illustration: Fig.102.Sighting Along the Sole of Jack-Plane.] The splitting of the wood in advance of the edge is also prevented by the breaking of the shaving as it hits against the cutter or its cap.
Hence the advantage of bending up and breaking or partly breaking the shaving as soon as possible after it is cut.

This shows why the cap is set close to the edge of the cutter.

Another reason is that it thereby stiffens the cutter and prevents "chattering." If a thick shaving be desired the cap has to be set farther back.

In a smooth-plane 1/32 inch is enough, in a jack-plane 1/8 inch is often desirable.

The following are the planes in common use: The _jack-plane_, Fig.