Unable to form a very simple closed sketch

[JishnuM]

I am a very beginner to Fusion 360, so sorry if this is a very dumb question. I am attempting to make a tab for a lid, two of which I have done on the sides, and two more which I would like to create on the top and bottom. For this, I offset a plane to the desired length, then created a sketch on the plane. However, when I go to create a line on the plane, it makes these purple lines. If I am on more than one of the lines, the sketch does not close or is not recognized as a plane. But, if the sketch starts and ends on the same line, then Fusion recognizes the face. I have attached a photo below which shows the offset plane, as well as examples of what does and does not work. When I am creating the sketch, I do use side view, by the way. Is there any way to fix this? I wasn't facing the problem on the sides, although the sides are a lot straighter.

[davebYYPCU]

For some reason you have 3 short purple lines, 

(normal) would be one long one from the top face of the tray.

So purple lines are fine to use but you need some small lines joined to their end points, over those two gaps,

then the outside section of the sketch will shade blue, and you are right to go.

When you get lazy, a centre line and half sketch will become an option (design dependent).

Might help.....

[TheCADWhisperer]

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

First thing I notice is no dimensions on your sketch?

The purple lines are Projections of these edges into your sketch.

Simply sketch a line from point to point to close the obvious gaps in the sketch.

...or...

Project these two missing edges into the sketch as well to close the gaps.

[JishnuM]

If you were to project the other edges, would show up (when 3D printing)? Also, wouldn't connecting the ends with another line make it a separate body?

[davebYYPCU]

No, and No.

Sketch does not go to a 3d printer, just bodies, so making the tab on the tray, as New Body, makes 2 bodies, as Join keeps all of the shape as 1 body.

But you can not make the new shape until the blue shading is made with a sketch and closed outline.

Might help.....

[TheCADWhisperer]

One word - observation. 
What do you observe if you take these actions that you question?

Why did you not Attach your file here?

[JishnuM · Accepted solution]

Yeah, I did end up trying it. It seems to be part of the same body. I didn't do it at first because I thought I might miss something.

Here is the file, by the way. I had just forgotten to do it. The piece I was talking about has been extruded in this version, as I was working with the design. You could go back to the sketch if you wanted to, though.

What I did, in the end, was unlink the projections (the purple ones) and connect them as a single line. It is showing up as connected, so I guess it works, although I still don't know why the projections weren't connected in the first place. 

Thanks, everyone, for your help!