Shodokan Aikido (also called Tomiki-style Aikido), because it was was founded by Kenji Tomiki Sensei, divides its Aikido techniques into two groups. The old and the new.
The new ones that are safe for free practice, at high speed and with full resistance by Uke were recorded and passed on through the Randori no Kata, which is also referred to as the Junanahon no Kata, the Kata of Seventeen.
This contains a total of 17 techniques, 16 Aikido throws and one armlock hold that Tomiki Sensei and his assistant Hideo Obah decided were safe enough to be performed in randori free practice or even in competition (shiai), just as Judo is taught and tested.
The older, traditional Daito Ryu jujitsu type Aikido moves were carefully preserved in the Koryo Katas, which were put together by Tomiki Sensei and Obah Sensei.
I knew the old-style katas as Dai Ich, Dai Ni, Dai San, Dai Yon, Dai Go etc. But actually those are the simplified names. For example, the weapons kata, Dai San, should actually be referred to as the Goshin no Kata. Dai San just means ‘Big Number three’, which doesn’t describe anything useful.
The Goshin no Kata is a self-defense kata that includes empty-handed kneeling techniques (suwari waza), then standing, then defence against a tanto knife, a bokken (Japanese hardwood sword) and finally a jo (short hardwood staff).
The Japanese wooden sword and the short staff are not just training tools, they are very effective weapons, quite capable of killing even an opponent armed with a live (sharp) sword. In fact, the jo staff was one of the tools that the Japanese police force would use to overcome and arrest sword-wielding swordsmen who were causing trouble. Naturally, they would usually do this as a team, but a jo can beat a katana if the user is skilled enough. The hard wood can reputedly even break the blade.
The Goshin no Kata also ends with Tori (the defender) demonstrating Jujitsu type defense techniques. But when the Jo is grabbed by Uke (the attacker), then the defender performs some offensive techniques instead. This is not stuff for beginners.