Item schticks are normally purchased one-by-one, like other schticks. but there are some exceptions to this rule.
When you purchase an item schtick, you get the ability to use that schtick during a session an unlimited number of times. But certain items, such as Potions and many Gadgets are one-use.
In such cases, you can bye an Item Pool. An item pool represents a pool of resources that you can tap. Unlike an inventory list of normal schrticks or gear, you do not have to decide exactly which props, potions or gadgets your character is carrying. Instead, you get to make a list of four times as many items as you have purchased, but you are limited to using a number of these items equal to the number of schticks you have in the pool.
Jennikki has an Item Pool worth two schticks. Her pool consists of Blinding Egg, Caltrops, Cutwire, Disappearing Powder, Firepot, Rope Ladder, Truth Drug, and Climbing Pole. During any one session she may use two of these items - or perhaps the same item twice. She cannot decide to have a Ninja Scabbard, nor can she use three blinding eggs in the same session - at least not without a montage and the GM's permission.
In certain cases, when a character hasn't been using the items in his pool during several sessions, the GM may be lenient and allowover-use during a single scenario.
You can also use your Item Pool to reduce the difficulty of Tinkering.
You can only use an iotem from your item pool once during a particular session, so continuing effects, like a MasterBlade do not work well as a part of an item pool.