We're going to make a clock now and I'm going to start off making the hand using symmetry. I've drawn half the hand using the Pen tool.
Half clock hand shape
I now want to make a symmetrical copy so with this object selected, go to the toolbar and find the Reflect tool.
Don't click and drag the object with this tool, even though it seems like the right thing to do because you'll end up with half a clock going all over the show. We want to be a bit more accurate about this, so we are going to place the point of reflection on the page where we want the object to reflect across. To do this, hold down the Alt key and click in the area that you want to reflect across. Illustrator will then give you an option box and you can experiment with any other angle reflection, horizontal or vertical. If you switch on the Preview button you can see what you're going to get. When you're happy with what you want, click Copy (not OK).
We've now got 2 parts of our clock hand and we want to then join them together. Select the top 2 points using the Direct Selection Tool. If you were to go directly to Object > Path > Join it would give you a straight line between those 2 points. Obviously not what we want for a nice sharp clock hand. Instead, go to Object > Path > Average. This will move the 2 points on top of each other.
Once you've moved the 2 points on top of each others, you can then use Object > Path > Join. Try this on the bottom part of the clock hand as well.
Try the same on the bottom line.
Remember to use the Direct Selection tool and not the Selection tool for both of these. Experiment with that too and see what you get!