How do I 'debug' a sketch

[johndcaswell]

I am very new with Fusion, and am trying to use it to serve as a source for a CNC that I have. 

I am trying to design a Backgammon surface that is quite a complicated series of traingles and lines.  I have created what looks right using lines and elipses that should create a constrained shape, but Fusion does not recognise it as a surface, so somewhere there are some lines that clearly do not meet.

Is there any way that I can find out which lines do not meet, short of trial and error?

[davebYYPCU]

It’s called divide and conquer, 

Draw a temporary line across the whole sketch, if you receive new shading in the sketch, then there is no leak in that shaded area.  Move this line to identify where the leak is.

There are 3rd party sketch checkers in the App Store, I don’t have any so can’t comment on them.

Do you have Snap turned on? (Helps)

Do you have Snap to grid turned on?  (Useless for me.)

Might help....