the first limb 88 of the arm 86 is a sliding fit in the groove 84. the first limb has a slot 89 formed in it which can receive a locking screw 91 to lock the arm against sliding in the groove in the plate. a large-scale project is likely to be required in this area in the near future. with the huge amount of leads to follow in this case, this is going to take a little longer. they had to discover each other and had to come to terms with the lives they had left behind. 