Many Samsung devices can be placed into download mode using a USB Jig, which when plugged in, allows users to ODIN restore a factory ROM from what would normally be a hard brick.

Motorola devices and, as it happens, the Amazon Kindle Fire, have a similar option called the factory cable. The factory cable, as explained by the Team Black Hat:

Unlike a normal USB cable these cables are wired in a way that compatible Motorola phones recognize as a "factory" programming cable. This allows the phone to power up and be flashed without having a battery in the phone. Depending upon the model of the phone, it may also boot up differently than it does with a normal USB cable.

And, much like the Samsung USB Jig, it'll help out those who have hard bricked their devices. XDA Senior Member SikYou has written up a brief explanation of the attempt made to create such a cable and from that has spawned an entire discussion, which slowly but surely details the full instructions to creating your very own factory cable. In his words:

There is a lot of information floating around about the factory cable but there doesn't seem to be a thread dedicated to the topic. I bricked my device today so I need to make a factory cable. I tried making a cable but I f'd up the soldering job so I am awaiting delivery of a breakout board. I just wanted to gather some information here on the topic because there seem to be a lot of bricks popping up around here. So for now I am going to post what I know and ask a few questions here and there so that I can get my cable done and hopefully help someone out along the way.

With some contributions from several other XDA Forum Members, including MayfairDROID, pyrostic and teookie, the whole process is pretty much outlined for anyone who wants to give it a shot. However, it should be noted that an improperly made cable could damage your device. So proceed with the utmost caution if you intend on making one and, of course, it's no one's fault but your own if something goes wrong.

Head on over to the Amazon Kindle Factory Cable Thread for additional information and to get started. You may need to read a few pages in to get all the info, but it is all there.