Tonneau cover locking spring clamp

A tonneau cover system for a cargo box of a pickup truck, said tonneau cover system comprising:

• a framework having a cross bow member supporting a cover, said framework being positionable generally over the cargo box of the pickup truck;
• and
• a locking spring clamp assembly having:
• a linkage member coupled to at least one of said framework and said cover at a connection location along said linkage member;
• a latch housing slidably coupled to said linkage member, said latch housing having an engaging member operable to engage the cargo box of the pickup truck in a latched position;
• a first biasing member urging said latch housing into said latched position;
• a locking feature releasably coupling said linkage member and said latch housing into a locked position, a distance between said connection location and said engaging member being generally constant in said latched position and generally maintained by said locking feature in a locked position.