If I click to draw a line, it draws, but when I double click at the end of the line it does not finish

How do I change the width of the line?

There are basically 3 tools to draw a "line".
On the other hand, technically it's another one that creates line objects, which is the connector tool.

So you can either use the
pencil/freehand tool or the
pen/Bezier tool or the
calligraphy tool

Each of them can create paths.
Are you using the pen tool?
It is made to register new nodes on the path until you press Enter or click on the starting node of the path.

To change the width of the stroke, open the fill and stroke panel (Shift+Ctrl+F) and at the third tab you will find the settings.

Using pencil mode how do I create straight lines

With sketch mode and ALT, the move tool is sometimes activated

By clicking with it at the beginning of the stroke and at the end of it, you can create a two noded path with two segments.

Other than that, I don't know how it would draw straight segments /or why it should.
If you want to use it because of the various shape options of the stroke made, you can add those to simple paths made with the Bezier tool.
As a pattern along path live path effect.

A simple search of the forum would have turned up an earlier version of this: http://forum.inkscapecommunity.com/inde ... ;article=7.

As I mentioned in another one of your messages, when it starts to look like someone is not taking advantage of the links to the manual and other resources, or even searching the forum before posting questions, some people, who might initially have wanted to help, lose their patience, and give up. I'm at that point now, and won't be even reading your future messages, much less answering. Judging by a couple of other replies to some of your messages, other members may not be far behind me, in skipping your questions.

You probably have not seen this. Might be a good idea to read it: viewtopic.php?f=5&t=745

If you are not interested in helping then that is your decision - I don't need to know

You may or may not have noticed that I'm officially a moderator in this forum. Although realistically, I haven't done any moderating lately. But as, I suppose you might say, a senior member of the forum, I'm trying to inform you how we generally approach answering messages, when people ask for help here.

Generally, we like to help people who show that they've made an effort to learn on their own. Generally, we guide you to the resources you might need to solve your own problem. If you consult those resources, and get stuck, we still are glad to help you sort it out. However, you need to provide a lot of details, so we know exactly what to say to you.

So for example, the message where you said something like "I found the snap control bar, but nothing snaps" -- I was happy to see that, because you found the snap control bar on your own, and are trying to learn how to use it. But there could be a hundred reasons why the snap isn't happening. We would need a lot more details to be able to help.

Regarding this particular thread -- You've been given a link to the manual, at least 4 times, among several other resources, considering all replies in all the messages you've posted. Yet rather than look in the manual to learn how to draw Bezier curves, you post in the forum. This does tend to irritate some people (at least it irritates me).

Anyway, my intent in posting this message is to try to let you know how generally this forum operates. I'm not trying to intimidate you, or insult you, or start trouble. I'm just trying to explain how you may receive the best possible help in this forum. The link I gave you to this topic: viewtopic.php?f=5&t=745 explains basically the guidelines for how to use this forum.

You said you were not going to read or reply to my responses.

You have no idea what I have read, or not read. What I understand from reading, and do not understand from reading.

Maybe I have read, do not uderstand, and, therefore, post.

I do not expect to hear from you again. That was your decision, not mine