Squares squares everywhere but no ‘snap to grid’ to be seen
When embarking on frame hanging venture try not to be too vigilant with the arrangement, there isn’t a set rule for layout. It is your art, your posters and your home so make the artistic array speak to you, it can be surprising how much one can judge on impulse and natural composition. Snap to grid if it works for you but do not fear the medley of positions, after all a nail in the wall need not be permanent. Do remember that a spirit level is your friend!
(If in doubt use pieces of paper cut to the size of your frames to stick on the walls to achieve the composition you desire before hanging)