iSHSHit is very straight forward and simple to use. After installing it from Cydia, just click on the save icon at the top right corner, and wait for it to save your SHSH blobs to Cydia. Once your SHSH blob has been saved, you will get a message as can be seen in the screenshots below.
In case you don’t already know, saving SHSH blobs have proved to be very useful for downgrading to older firmwares. Recent tweets from Comex suggests that they will also be required for untethered jailbreaks in future.
Here is the official description:
iSHSHit allows you to back up device firmware SHSH blobs from Apple directly on your device for later downgrading. It automatically uses the Cydia On File service in the background, so it’s a great way to ensure that your SHSH is stored by Cydia. iSHSHit can also email your SHSH blobs to you for more permanent storage.
You will, of course, need to have a jailbroken iPhone or iPod touch to install it. Follow our step by step guide posted here to jailbreak your iPhone, iPad or iPod touch with Redsn0w on iOS 4.2.1, or with Limera1n on iOS 4.1 if you haven’t already.
iSHSHit is available now from Cydia under the BigBoss repository for free.