This is a 100% true story. I had a hot girlfriend who used to let me tie her up on occasion. We had done some bondage several times in the past. She would more let me do it because she knew I liked it, as opposed to being really into it, and usually when we've both been drinking or feeling risquΓ©. But it was only occasionally, and she had no complaints about it. Sometimes she would manage to spit out a gag, or get free in some way, mostly because I would take it easy on her. We were together for several months, and for some reason I decided to take off the kid gloves and have some fun, at her expense. Thus, one day, to her surprise, I went all extreme on her, and it was awesome. I'm not sure what came over me. I was just determined to thoroughly tie her up.
After getting her naked, I tied her hands behind her back by the wrists. Then I sat her in a straight back chair. I put her tied hands and arms behind the chair back, then tied her left ankle to the left back chair leg and her right ankle to the right back chair leg, effectively spreading her legs wide. With her legs pulled back like that, only her toes and the balls of her feet could touch the ground, and because they were tied to the the rear chair legs, she was forced to sit right up against the chair back. That, combined with her arms behind the chair back, made her look like she was sitting up straight at attention. Then I tied a length rope to her bound wrists, and tied it to the support bar on the bottom of the chair so she couldn't lean forward, forcing her to sit up straight and making it so she couldn't move her arms much at all. I used another length of rope to tie her elbows together - mercifully not actually touching, but close. It had the effect of making her beautiful breasts stick out, looking like she was proudly sitting at attention with her legs spread, chest out, straddling the chair, to which she was effectively bound and anchored to.
Then I took the panties she had been previously wearing, which were thankfully full cotton bikini cut, reversed them and bunched them up, keeping the crotch on the outside, and stuffed them deep inside her mouth, making sure to get all the material behind her teeth. Thanks to the fact that she didn't wear a thong that day, they fully stuffed her mouth. I smelled the crotch before stuffing them in her mouth and was happy that they had her "scent" on them (a polite way of saying they smelled like panties that had been worn all day would smell). I used a wide elastic bandage to hold them in, wrapping it tightly between her teeth and around her head several times before knotting it tightly behind her head.
I very much liked the way the wide elastic bandage held the panties tightly in place deep in her mouth and held her mouth wide open, with her pretty lips pursed out above and below it. It was so tightly wrapped that it distorted her pretty mouth and face, and god did she look gorgeous like that. It would have been plenty secure like that, but to make 100% sure she couldn't spit it out, I tied a length of rope behind her head, under the layers of elastic bandage wrapped around her face holding in the panty gag, and tied the other end tight under the rung in the back of the chair, pulling her head back and forcing her to look up at the ceiling.