How to create an effect similar to attached.

jp91306, Hello.

I think this illustration is made up of straight lines, not patterns.
If it is a pattern, the edges will be cut off. I think the straight line ends in this illustration are square.

But I don't know how to make this easy using effects.

I will make one by one.

A rough flow is to cut a straight path with a pathfinder.

Prepare a path of the same width shifted by the width of the line.
(The thin part is expressed by only one pass, and the thick part is expressed by arranging two.)

Prepare the shape to cut out. (The middle is not for clipping)
 

Make a thin part.
This is made with PathFinder's OutLine.

Make a thickened part.

Duplicate everything and rotate 180 degrees.

That's all for my work plan

I am Japanese, so if my English is strange, laugh and forgive me.

You could fill a shape with a striped pattern.