Vertical Line Divider

Site URL: https://rituelstudio.squarespace.com/manualtherapy

I would like to place a vertical line to divide the page left to right - the same as I put the horizontal line dividing top to bottom.  Is there a way to add this using CSS?  On my page, it would divide the section Pilates from Gyrotonic.  Hope it makes sense.  Thanks!! https://rituelstudio.squarespace.com/manualtherapy

div#block-5dd94ce65fd0b302beff6cbb {
    border-right: 1px solid black;
}

Add to Design > Custom CSS

That didn't work.  It just writes the text at the top of the page.