Sounds like you are talking about a baby stay.
Does your boat have forward lowers ? If not then yes,definitely a baby stay, particularly as you say its attached to the (I presume you meant to say cabin top not sole) just aft of the hatch.
Here's another thread...
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
"Those are my principles, and if you don't like them... well, I have others." Julius Henry Marx.