How To Align your Platen and make sure it is Straight???

I use a drywall T-square. You can get one from a hardware store for around 30 bucks. I got a long one and cut it down to the length that I need.

when I set up my press I get the platen so the screen falls on it how I need it to roughly depending on the design, I then mark out my platen how I need to. I will then place the film positive on my platen and I will Square it on the platen. I will then make my screen fall to the platen correctly. As long as you load your shirts to the marks on your platen correctly they are in the right spot. maybe easier ways but this works for me

I use a t-square to square the platen to the press every time I reset the platen position. Then before you put ink in the screen, center it on the platen and use your square to be sure the image is also square to the platen. Never had any problems.

Draw a centerline on the platen in Sharpie and align it to the arm by eye. If you don't trust your eye and the top of the platen is square you can use a T-square. You could also use a laser level.

Make sure your brackets are parallel to the centerline on the platen.

I draw a center line on the platens first. Drop the arm down on the press put the drywall t square in the press head, align the platen centered and front to back. I do this for all the platens then for all the heads to make sure everything is the same. I very seldom move my platens, so some kind of a registration table is a must.

^ +1

I would mark the platen, as that's where the shirts/art will be

We draw a centerline on the platen, (depending on art work might draw 2 one for horizontal and one for vertical.) Then on the artwork itself we have Targets located on the center line of the artwork. Burn screen line up the target to the centerline done. If there is multiple platens just align the rest of the platens to the target.