Add a thick line across the whole page

Hi,
I would like to add a thick horizontal line across certain parts of my website. So that it sections items off.

At present I am just using ————————————
to section things off which doesn’t look very good.

https://www.aposrecruitment.co.uk

My website is above and as an example on the HOME tab is hwere I would like to input a solid thick line or two.

Thanks for any help,
Rob