Reddit mentions of The Anal Hook

Dont touch it with your hands

The rope is attached to a hook with a ball at the end that is in her ass.

Edit: something like this

also to answer /u/FHBruce 's question, there is actually a common sex toy that fits his description.

It's called an Anal Hook It's an amazon link but NSFW just in case.

Amazon!

You should look into something like this

http://www.amazon.com/Master-Series-Steel-Anal-Bondage/dp/B007YUX6UA

If you could find one that is a little shorter I think it would match more of what you're looking for. You could buy a tail separately and attach it to the ring end.

https://smile.amazon.com/Master-Steel-Anal-Bondage-Hook/dp/B007YUX6UA/ref=pd_bxgy_121_img_2?_encoding=UTF8&pd_rd_i=B007YUX6UA&pd_rd_r=7PXHF6MKFD10JH3966F4&pd_rd_w=2zVV7&pd_rd_wg=AMQYH&psc=1&refRID=7PXHF6MKFD10JH3966F4

or

https://www.amazon.com/Miss-Darcy-Arrival-Fetish-Bondage/dp/B00E4GURE0

or

https://www.twistedmonk.com/products/ass-hook

Dead bat

Chocolate bugs

Nipple suction device

Butt hook

Speculum

ANAL speculum

"Magic hand"

Giant inflatable dildo

Enema kit

"Knuckle up" dildo

Finger tentacles

Yodeling pickle

Inflatable toast

Bacon lip balm

Coyote urine

1,500 live ladybugs

Canned unicorn meat

Weener Kleener soap

"Liquid ass"

Macaroni and cheese air freshener

Fetus doll

Oh man, this was fun. I had to eventually just make myself stop looking because I literally could have linked about 100 things.

http://www.amazon.com/Master-Series-Steel-Anal-Bondage/dp/B007YUX6UA
What you need is a anal hook. This will curve up and give you the right position.

It's just called an anal hook. You can get them almost anywhere, even amazon lol, here's a link

Does your grappling hook look like [this?] (https://www.amazon.com/Master-Steel-Anal-Bondage-Hook/dp/B007YUX6UA)

Ok, here you go. Master Series The Steel Anal Bondage Hook https://www.amazon.com/dp/B007YUX6UA/ref=cm_sw_r_cp_api_i_yYjmDb2N153VZ

This could be what you are looking for. NSFW butt hook