Jars of sturdy glass and with wide-mouthed tops are called canning jars and are made specifically for preserving purposes, with lids and separate screw bands that form the necessary airtight vacuum. Be sure to use only lids and bands manufactured for the jars you are using. Do not reuse lids, which cannot form a seal once they have been opened. Glass jars can be used as storage containers for sauces, condiments, and other foods that do not require canning.