Lower the load onto the stack by adjusting the boom angle and retracting the boom slightly if necessary to position the load.
Note: Any time the boom is retracted in these circumstances it will also move downwards. Imagine that the pile of pallets in the picture above were a scaffold on a building site and the telehandler has just placed a pack of bricks on it. The downwards movement of the boom can easily break the scaffold, (or whatever is there), and cause a serious accident. It follows that great care should be taken under these circumstances.
In order to minimise this problem, many telehandlers are designed in such a way that the forks can "ride up" a little if this happens. The picture below shows the arrangement on this machine.
The forks are mounted on a bar which runs across the machine. Note that it's fitted into a slot which allows a small amount of movement upwards in the event of the forks dragging on something.