Humminbird 1158c Combo Installation And Operation Manual page 45

Hold the ratchets on the transducer knuckle with one hand and fit the pivot arm over them until
it snaps into place with the other hand. Refer to the illustration.
Transducer Knuckle Positions
Ratchets Placed in Position 2
Rib
Knuckle
Rib at
position 1
Fitting the Pivot Arm Over the Ratchet
Bead
Ratchet
33
Ratchets Placed in Position 1
Transom Mount - DualBeam™ PLUS
Beads
Ratchet