The stem sockets allow the keel rollers to be adjusted up and down to suit the boat shape.
Fabricate 2 stem sockets as per the plan below. Predrill the sockets with a 13mm drill prior to welding the 12mm hex nuts in position.
Fitting the stem sockets is pretty self explanatory.
Align the front keel roller stem socket so that it is central with the drawbar and flush with the top of the drawbar brace.
Square the stem socket with the drawbar brace to make sure it is straight up and down and weld into position.
For the centre stem socket, you may need to grind and flatten the weld joining the cross members together to allow a nice flat surface for mounting the socket.
Align the centre of the socket with the centre of the cross member and the outside edges of the socket are in line with the top of the cross member.
Check that the trailer is level across the width of the trailer and then level the stem socket vertically.
Once happy with the position of the stem socket, fully weld to the cross member.