Be Careful - For those bloggers, like me, who insist on using the Old Post Editor, the new feature Jump Breaks is still NOT available to you, although you can still use html code in your Template.
Also, be very careful you do NOT get confused, like I did, when reading the Blogger Help article, or the Blogger in Draft article, where it says:
"If you don't use the new post editor, you can still insert a jump break in Edit HTML mode by adding code where you want to position the jump break."
Unless, you work in Blogger in Draft, or use the New Post Editor (see: Settings - Basic / Global Settings / Select Post Editor), you can't just add a snippet of style code via your html Post Editor, in OLD Editor. Don't worry, though, it's easy enough to do in the NEW Editor ... just place a jump break in your post, click on Edit Html, and place the code where you want it, just like in the following image ...
* NOTE: This image shows the code in the NEW Html Editor - (Image copied from Blogger Help - for educational purposes only ...). Until Blogger iron out any, and all possible glitches, and stabilise NEW Editor, and add Spell Check, I won't be using it.
Once you have placed the Jump Break in your Html post, you will see a grey/gray line in Compose mode, where the Jump Break is positioned. You are then ready to Publish.
Don't make THIS mistake ...
If you add the code into your OLD Post Editor, you get formatting problems after posting. For example, the sidebar will go crazy, Page Elements will appear anywhere, the Read more won't appear, etc.
If you read some of the articles about Jump Breaks, you'll also notice that the wording can be changed - personalised, if you will, to suit your style.
By navigating to the Layout | Page Elements tab. Click Edit on the Blog Post widget, and then change the Post page link text to whatever you'd like ... see: Blogger Help article "Creating After the Jump summaries".