Rehang the pieces to be bound off together, right sides together, on the back bed needles. Set the beds so the needles alternate (like you would for full needle rib). Back carriage set at an average 1X1 ribbing tension for the yarn (I use 3 for most of what I do). Front bed set one number lower than back bed. Both carriages set to knit. Bring up needles on the front bed to correspond to those in work on the back bed.
Thread the carriage, and knit one row across. The front bed needles now all have loops in them. Pull all the back bed needles into hold position. Then carefully drop the front bed all the way down, keeping those loops on the front needles. Latch tool bind off only the back bed needles, leaving the work hanging by the front needles as you work across. Those front needles are acting as your gate pegs that you don't have.
When all the back bed needles are bound off, take the front carriage across by itself, with the needle return buttons down. This drops the work off the front bed needles and you are finished.