Saracen Gull wing Hitch Lock

tigerfish

I was given one opf these by my dealer when I changed the van last September. My seven year old Alko One did not fit the new head.

 But its been a complete disaster. I think that ive managed to get it actually on and locked once' in the dozen or so times that Ive tried to fit it.

I suspect that its somethng to do with the Allen key and sliding lock system?

Any advice gratefully received or its going to get free flying lessons!

TF