The héng stroke is also a character in Chinese, which means that it stands on its own and has a meaning in modern Chinese language:

You can vary the lengths of the héng stroke within a single character. For example, in this character, the top héng stroke is shorter than the bottom one:

Here's another example of a character in which the lengths of the héng strokes are varied:

As you can see, each diagram tells you the stroke order for each character – that is, the order in which each stroke in the character is meant to be drawn. Knowing stroke order is important, especially as the characters you're writing start to become more complicated. Stroke order can helps you to organize your strokes so that your characters look more like those written by native Chinese speakers.

I recommend that you follow the stroke order for each Chinese character, so that you get used to drawing the strokes in the proper order. These three characters provide an example of one rule of thumb that can help you memorize stroke order: Generally speaking, in a single character, the strokes tend to be drawn from top to bottom.