Having covered hand planes, you need to know how much material to take off. this is where your Marking Gage comes into play. Also the marking gage is usually one of the first tools someone makes for themselves so…
Marking gages are super simple to make, and you will need a couple during your career.
They have three essential parts, a beam, a fence, and a locking mechanism.
the beam is a stick of any consistent dimensions that you like. Eg. 1″ square or 1″ round… and has some way of leaving a mark on the wood, a pin to scratch, a knife to cut, or it might have a pencil holder built in.
the fence is a block of wood that the beam passes through and the locking mechanism is housed in.
And the locking mechanism could be a screw, a lever, or some sort of wedge. By far the easiest one is the the japanese wedge, and the trapped or french wedge comes close for simplicity.
So I will outline the making of 2.
I start with the fence. And make the wedge hole first… Use find a scrap @ 3″ x 3″ or 3″ x 4″… Find the center and Draw a 1″ diameter hole, or square.
for the gage on the left, draw a line across tangent to the top of of the circle with your square. bring the line around the side, and find the center. drill a 1/2″ hole all the way through to the other side.
Then drill a 1″ diameter hole as square to the face as you can. (drill presses allowed).
If you are going to use a square beam then use a square to scribe the lines and cut the hole into a square with your chisels.
to make a beam you can get a 1″ hardwood dowel or use a rounder plane to make one, sand it until it just slips through the hole, or plane a 1″ square until it just fits the square hole.
you can use a nail for the marking pin, but broken drill bit of less than 1/8″ diameter works better. drill a smaller hole and drive it in. If it is going in too hard make a saw kerf with a very fine saw up to the hole.
you can make a flat on top of the dowel type if you like, or not.
the wedge on the left hand model is a dowel with a cut out as shown that goes @ half way through. tapping one end will lock it, and tapping the other will free it. And it can’t fall out as long as the beam is in place. This is a Japanese style gage.
the french wedge is a bit trickier, it needs a mortice that is the size of the knob on the small end, see how the mortices intersect in the illustration.
Or you can orient the wedge parallel to the beam.
there are many different types or styles of gages, make what you think will be most useful for you.