If you drive in two nails or large screwnails at an angle.....thereby bridging the gap between fascia board and underside of sheet............this will enable you to put a small handful of stiffish mortar in the gap. The nails will provide a key to hold mortar and it`s cheap.
Use a gloved hand to apply mortar.........it`s actually quicker than a trowel.
Alex
Use a gloved hand to apply mortar.........it`s actually quicker than a trowel.
Alex