turning a line into a solid

I draw lines that project from one solid to the other.

When I render, they don't show up. can I make a solid by using that line?

Extruding the lines will convert them to surfaces.

Can you provide a drawing or an image so we can see what you are doing?

The gif is 2 sundials

The green one wit purple numbers and a blue stick in the center is an armillary dial. the blue stick casts a shadow on the purple number

The one below it is an analemmatic dial. You paint it on the ground. In the summer, stand on the mark "Summer" and your shadow will point to the hour number in blue

I need to project lines from the armillary dial to draw the other one.

At the moment I'm extruding 1mm diam circles to make cyliners

If I extude lines. can I make them wider (1mm) to make them stand out?

Yes you can.Its better if you extrude a circle and the lines would be your path.

These projections are at unknown angles. I need to project first before I can find the angle and even then I don't know (have never tried) to read it

It's easy to draw a circle in a standard plane. I have never tried to extude a circle to follow the path of a different plane. Can I?

Yes, you can.

Wow! I feel like a bonehead. It was right in front of me all along

Yes, it was. Seek and ye shall find.

These projections are at unknown angles....

 

It's easy to draw a circle in a standard plane. I have never tried to extude a circle to follow the path of a different plane. Can I?

Doesn't matter where the circle is - it can be anywhere.

Use Sweep instead of Extrude. Sweep command will automatically line your circle up on path.