Take a chisel or a center punch.
Jack up one side, or both sides of the front tires, one side at a time is okay too.
Get Your hand wrapped around the punch/chisel, place the sharp edge against the tire, Spin, or have someone spin the tire while firmly holding the scribing device. Scribe a line all the way around the tire, repeat on the other front tire.
Drop the vehicle back to the ground. Half way up the tire, measure the distance between the scribe marks, front or back, then if you measured at the back, move to the front and measure the distance between the scribe marks.
The difference in the measurements will be the amount of toe in, or, toe out.
Books gives the amount of toe in.
Usually about a 1/16th to 3/16ths toe in at the front will be good.
A better more solid scribing device can be built.
Piece of flat, six inch square, smaller or bigger dont matter. 1/8th thick is okay.
In the middle, weld on two upright bars, about six or so inches long, 1/8th or 1/4” thick is fine. At the top bore a hole through both bars at the same height on each one. Maybe an inch or less from the top.
A pin to fit the holes.
Another flat bar, bring one end to a curved point like the end of a knife blade, so it will be sharp enough on the tip to scribe a mark.
About half the length drill a hole the same size as the hole through the two posts.
Set the sharpened bar between the posts place the pin through the one post, through the bar, through the other post so You have some round stock hanging out through each post and weld the sharpened bar to the round stock.
The two posts should be at a proper distance apart so that the sharpened bar dont drift between the posts.
A hole drilled through the but end of the sharpened bar, a small loop on the base and a spring attached between the bar and the base will apply tension to the tire while spinning the tire to scribe the marks. Kind of like a teeter totter.
If I was any good with some of the drawing apps I could draw it out so I hope You understand the building instructions.
Basically it is two posts, with a pivot bar between them. One end of the bar is sharp, other end has a tensioner spring between the bar and the base so the spring applies pressure to the pointed end to aid in scribing the mark.
Oh yeah, the curved side of the pointed blade goes downwards so that only the point is against the tire.
I dont know how else to describe it. I have used them.
The DOT even had a factory made measuring rod of square tube, one fit inside the other with wing bolts so once set they would not slide inside of each other. Both ends has an upright pointer, one pointer had marks, 0 being the center and 1/32nds “ marks out from both sides.
The line on each tire was scribed then the measuring stick slid up so the pointers were at the tires, one end non adjustable set on its scribed line, other end adjusted with the pointer on its mark and the measure gauge set on 0. Then the stick moved to the other side, non adjustable pointer set on its scribed line, other end with the measurements set up to the tire, then, the end with the 0 and measurements adjusted to the scribe and how far off from 0 that the pointer was at is how much toe out/ toe inn there was.