Seoi Otoshi

Seoi-otoshi, in my opinion, is best performed as mixture of throws rather than a throw in it's own right.

1. Seoi-nage / Tai-otoshi cross.
Seoi-otoshi can be performed with either an Ippon-seoi-nage or Morote-seoi-nage arm movement (or slight variation of either if you prefer). Move into the Seoi-nage position, but instead of bending legs, attack with your legs like a Tai-otoshi.

2. Dropping Knee as above.
As above, but in a right handed technique, place your right knee on the ground. This would be considered Kata-hiza-seoi-otoshi.

3. Dropping knee by itself.
Attack in a Seoi-nage of your choice, and drop onto one knee inside of your opponents legs - this technique relies more on the drop of the technique than the above two.

4. Dropping Seoi Nage (Ryo-hiza-seoi-otoshi).
As the above three, attack with a Seoi-nage with your arms. Drop inside your opponent on both knees (to save your own knees try to land between your shins and your knees), driving your right shoulder to the ground. This technique now has it's own page, due to the new BJA syllabus.

5. Kata-hiza-seoi-otoshi
As 2, but drop onto the left knee.

Currently, due to the new rule changes, only the over 12's are allowed to perform versions 2, 3 and 4.

This technique is also known as Morote-seoi-otoshi and Ippon-seoi-otoshi (Differentiating between the two different arm movements) and Kata-hiza-zuki-seoi-otoshi (distinguishing the use of only one knee).