To accurately identify which arrow on the diagram represents the Senate's check on executive power during the appointment of an official, you would typically look for an arrow indicating the Senate's action of either approving or rejecting presidential appointments. This is typically depicted as an arrow pointing from the Senate toward the executive branch (the president).
If you have a specific diagram, look for the arrow labeled with terms like "Senate Approval" or "Senate Confirmation" and it should direct towards the presidential appointments. If you're unable to see the diagram, please describe it, and I can provide more detailed guidance.