This is seriously good, especially as it's such a potentially boring exercise. I applaud you for your patience.

This forms the basis of most forms of shading. Consistency is vital and this exercise was designed to show you that. Any variance in the gaps between lines, the pressure you apply to lines, or the straightness of the lines is immediately apparent, as they always attract unwanted attention. And none of yours do!

Here's a tip worth trying and that I think will help you a lot: If you are trying to draw two lines a pencil-width apart (or any narrow width), draw the first line and when you draw the second one, look at the GAP you're leaving and not at the line you're drawing. You are effectively drawing a white line between the two, so if you look at that the feedback between your brain and hand will be about the width of that white line and not about the one you're drawing. The same applies when you try to draw a line in between two others.

There are so few inconsistent lines that I'm going to ignore them, their weight is remarkably even!, and the gaps between them hardly vary at all. This technique works best if the gaps are the same width as your lines - as yours are - so you remove 50% of the white in the first box and then incrementally reduce it further as you progress right.

This is a technique you'll probably never use again in its purity (unless you're a comic book artist), but if you imagine shading this way with no gaps at all, you'll see that it does form the basis for the majority of shading techniques, so it's one you need to be aware of. And to be aware of the need for consistency too.

This might help, too: LINEAR SHADING

You might have had problems - but they don't show. As far as I can tell from your image (which I finally gave up trying to fix ) this is near-perfect! Your midtone lines of shading taper to white at the left-hand side and should blend smoothly. And your lines of shading properly appears to follow the contours of the cylinder. None seem to remain visible after blending, although any that survived would read as surface texture.

Incidentally, if you were having problems drawing a downward-pointing arc, try turning your paper upside down. That way the arcs will follow the natural movement of your wrist. Personally, I never turn my paper, because I lose the "reality" of the subject I'm drawing. You risk it becoming a "drawing exercise" instead of the creation of a living form.

Your vertical black shading at the right-hand side is strong, consistent, smoothly applied, devoid of gaps, and lightens really well as it progresses to the left. Establishing that strong dark tone at the right hand edge certainly boosted the brightness of the highlighted left-hand side, which is what I hoped to see.

More viewing for you: CONTOUR SHADING


Personally, I only use 2B, HB and 2H. And to achieve really solid blacks, I layer HB over the 2B. However, my paper is considerably smoother than yours. And it's long-grained, so it rarely even lift a fibre, no matter how hard I grind the graphite into the surface.

This is my attempt at that house: TONAL SHADING

This is looking really good. Your darks are strong and solid, and you've chosen a good range of tones. But the cast shadows could have been darker.

Your shading of the roof and left-hand wall is smooth, with a hint of texture, which works well. The corner between the two walls displays outline, which is unfortunate. You could have easily drawn that wall dark enough to match the value of that line. Or, of course, drawn the line more lightly.

More importantly, the junction of the dark cast shadow and the edge of the roof is very soft. A hard sharp edge is what the eye expects to see, and it's a visual clue to the fact that the two planes are not connected. You could have used a hard black line to define that edge and then extended that line down to form the shadow.

THE RIGHT-HAND EAVE'S CAST SHADOW:
The right-hand eave's cast shadow is nicely diluted along its lower edge, which you would expect on a lighter wall that reflects light, but its upper part could have been darker. I also feel this wall could have been lighter, That would have increased the overall contrast. And it does seem rather odd that the underside of the eaves at the right is actually lighter than the wall below it -= given that the wall is receiving more light.

Incidentally, never mind what the reference might say. You need to interpret it in such a way that you're telling the viewer exactly what is going on. Which is what I think you tried to.

THE RIGHT-HAND WALL:
This is shaded with interesting a varied areas of tone and texture. I'll mention here that if you had shaded it horizontally you have to follow the perspective. In this case, that's more applicable to the left-hand wall. If the lines don't follow the perspective it shows a texture that doesn't conform to any wall known texture. The lines will look awkward and distract the viewer because they don't follow any expected pattern. The eye always looks for pattern and understanding and it's easy to unsettle it if you present it with something it can't match to it's known knowledge.