These are called QiSei. They are actually ancient martial arts exercise devices.
Parts needed:
1. 4' hardwood dowel cut in half. It should be between 1 inch and 1.5" in diameter, depending on what is comfortable for your hands.
2. Two 1 pound coffee cans (if you have been really working out 2.5 pound cans can be used).
3. 6 small wood screws.
4. Bag of ready mix concrete.

Poke a small hole in the center of each coffee can bottom. Use an ice pick or something else shrp to keep the hole small.
Poke another hole in the center of the end of each half of the dowel.
Screw three of the screws 1/2 way into the dowels, near the end with the hole. These will help keep the can from slipping.
Screw the last screw through the hole in the can into the hole in the end of the dowel.
Mix enough of the ready mix to fill both cans. Pour or spoon into the cans and let dry over night.

Each can & dowel should weigh about 5 to 6 pounds. Hold the dowel at the end opposite the can and do various wrist and arm exercises.
You can also hold in both hands and do two handed sword exercises. If you can't hold the dowel at the end, move your grip closer to the can until you are stronger.

See and for forms you can use with your QiSei.

Author's Bio: 

1960-1962 Kodokan Judo/Korean Yudo, gokyu; w/ Sensei Kim Young Chol (Queens, NY)
1962-1973 Furuya Ryu Kobujitsu (Jujitsu), nidan; w/ Sensei Kenichi Furuya & Sensei
Kenjiro Furuya (Queens, NY), with a gap from 1968 to 1971 due to service in the US Army.
1964-1973 Jujitsu & Shorinji Kempo, sandan in Jujutsu; w/ Sensei Arai, Long Island Jujutsu Academy (Queens, NY), with a gap from 1968 to 1971 due to service in the US Army.
1973-1982 Jujitsu & Hop Gar Gongfu & Qigong, yondan in Jujutsu; w/ Sensei Andy Garcia (Miami Beach, Fl.)
1993-1994 Jujitsu & Aikido, w/ Sensei Leoni Velasquez. (Hollywood, Fl.)
1996-1999 Chen Taijiquan; w/ Yan GaoFei under Chen QuanZhong. (Hollywood, Fl.), on and off due to work.

1999-2008 Qigong with Dr. Zhou Peigen
Additional Qigong training with GM Chen Quanzhong, GM Chen Zhenglei, Sifu Andy Garcia, Dr. Glenn Morris and Laosi Paul Chen.