The external handle extends inside the pen to make a loop around the sac. Pull on the handle to compress the sac towards the filler.
![](https://vintagependoctor.com/wp-content/uploads/2020/03/IMG_3354-1024x333.jpg)
![](https://vintagependoctor.com/wp-content/uploads/2020/03/IMG_3361-1024x796.jpg)
![](https://vintagependoctor.com/wp-content/uploads/2020/03/holland-saddle-fill-snip.png)
The external handle extends inside the pen to make a loop around the sac. Pull on the handle to compress the sac towards the filler.