BACKSTOP

A backstop is provided to attain prevention from contact between a spacer and a peripheral member. A rear jib backstop (60) for a crane (1) includes an outer cylinder (60A), an inner cylinder (60B), a spacer (70), a spacer holder (80), and a lock mechanism (90). The spacer holder (80) supports the spacer (70) pivotally and swingably about an axis thereof and allows the spacer (70) to fit on the inner cylinder (60B) to keep the rear jib backstop (60) from contracting in accordance with a change in a posture of the rear jib backstop (60) when a boom (16) rises. The lock mechanism (90) enables locking of the spacer (70) in such a manner as to keep the spacer (70) from swinging about a swing central axis (CT) in a state where the spacer (70) is located away from an outer surface of the inner cylinder (60B).