Segmented ledges on the grip guide the thumb and index finger into opposition, reducing muscle fatigue and improving control for users with limited dexterity.
Rotatable handles on a writing instrument enable selective positioning of the utensil, resolving the trade-off between device complexity and versatility.
A pneumatic ball spinning device suspends a golf ball on an air cushion to induce rotation.
A dual-structured sealing member combines a soft inner tube with a rigid outer hard tube to maintain airtightness around the pen tip.
Joint devices connect the cover and spine to securely fasten interchangeable ring pads, preventing instability during extended use.
A pressing pen positioning assembly uses a guide piece and sliding member to extend the refill.