I make a Dead-On rangefinder on any and every bow I hunt with (trad or compound) with 2 thin strips of white electrical tape on my riser.
If you figure out the AVERAGE size of the game in your area, it isn't hard to do and it works well.
If the average deer in your woods has a body that averages 16" from the top of their back to their belly line all you have to do is cut a 16" piece of cardboard and place it against your target. Walk back to the distance you are comfortable with - say 20 yards in this example.
Put one thin strip of tape on your riser and hold your arm out as if you are shooting, even better, nock an arrow and draw your bow while holding the tape marker along the bottom of the cardboard. In your mind imagine where the top of the cardboard will line up on your riser above this piece of tape and place your other piece of tape on that line so that from your chosen distance, the tape represents 16" at your draw length. Verify the placement a couple times to ensure that both pieces of tape are where you want it - you want both pieces of tape to hit exactly the upper and lower edges of the 16" cardboard which is the representation of the AVERAGE deer in your woods at whatever distance you picked; 20 yards in my example. Be as accurate as you can be. If you hunt in my home state of O-H-I-O, you will want a bigger piece of cardboard, if you hunt in Florida where I live now, you can use a smaller piece, the key is knowing the AVERAGE deer in your area.
When hunting, you can draw your bow and place the bottom tape on the belly line of the deer, if the deer's back is larger than the gap of your tape marks, it is closer than your 20 yard calibration. If the deer's topline is in between your two lines, you know the deer is further than 20 yards from you.
Be sure to use thin pieces of tape, I prefer 1/16" strips. Any smaller and they disappear during prime shooting light.
As an added bonus, I put my lower piece of tape EXACTLY where my 20 yard gap is on my bow therefore it serves 2 purposes - a range finder and a sight pin.
I love trad archery but I am not a purist.
Here is a SF riser that I love, it has a thick mark (my 20 yard gap) and two thin(ner) marks corresponding to 20 and 30 yards respectively per the average deer in my region. I may not shoot at 30 yards but it is nice to know where that 'distance' is for me to help determine if a shot has presented itself.
...now all I have to do is find the dadgum deer here in Central Florida.