Clampmate

Hi There,

I have recently been given a pair of 'Clampmates'. These are not the nice units used to assemble picture frames by means of tightening one central clamp, which then applies equal pressure to all four corners!! ( This type is easy enough to find on the net) No , these are a pair of black coated steel box section, about one inch across, and about three foot long There are a number of holes drilled through one side to the opposite side, and on the opposite side are three holes which are countersunk. there are two orange painted steel , box section units that slide onto the black sections. The orange pieces have what look like flat clamping plates and round tubes that can be screwed into the countersunk holes in the black box section. There is no obvious way to tighten the clamp!!!. Am I missing some bits? . Can anybody help me before I throw them away in frustration.

Thanks, Steve.