Thanks. ... I was actually thinking about when you had mentioned taking a sketchbook into the woods and sketching out trees that you saw and such...
So I thought maybe I should try sketching some skulls, and using an actual image so as to make sure I was getting all the elements correct and with more realistic details, etc. But it just wasn't happening. No matter how I attempted it. Tried working a basic outline and placing elements as they appeared, tried working from the center out. Nothing. I just couldn't fathom not being able to look at something right in front of you and have so much trouble just trying to get it even close. I just got aggravated after a while.
(Guess I should mention here that I don't think I've been in the best of moods here recently. Finding my patience wearing thin quite often and nothing like it normally is. - Think it's one of the reasons I wanted to get back to doing some Artwork and getting back to something I've always found relaxing.)
But your mention of using a ruler, reminded me of a guy I watched on YouTube some years ago. I was just watching some random art stuff, and happened to see his link with an image he did. So I watched as he meticulously worked the image, based off a photo he was working from. And he too said he uses a ruler to make sure he was getting everything down in it's proper place and have it exact. (It actually looked just like the picture when he was finally done, even the shading, but it did take him some time to get it done. Think he mentioned he was commissioned for it, so wanted to keep it completely accurate) But he also mentioned that if your not wanting to be that precise, you could use the pencil itself, simply using your fingers and the tip to get quick reference lengths, which made sense.