Originally Posted by Taipei Tony

I used to browse the Tern forums and this issue came up a few times.

There is a small plastic safety pin within the clamping mechanism. When you want to open the clamp, you need to press the little safety button which unlocks the plastic pin. It's very likely that your safety pin is broken.

Check out these threads:
http://www.ternbicycles.com/us/forum...-lever-tern-d8
http://www.ternbicycles.com/us/forum...e-catch-broken
http://www.ternbicycles.com/forum/th...ndlepost-latch