What does Odin's T-Flash option do?

According to this guide it writes the bootloader of a working device onto the SD card. This guide is a bit more detailed and describes it as follows:

T Flash option in odin is for Samsung boot recovery via sd card. This option is checked when we are going to make Samsung boot able sd card to fix or unbrick Samsung dead boot devices. In this case we must have Samsung original boot recovery.tar file for the exact model witch we are going to unbrick. We must have same and full working phone in hands. This option is used in new Samsung Qualcomm based models that allow boot from external memories. I will explain how to recover Samsung dead boot phones with sd card but in other post i will try to leave a link in this post. So T Flash option is to make a boot able sd card from full working phone to unbrick other Samsung phone.

How that's useful is described in a short guide here (in German). In short: Say you have a device where the bootloader is broken. But you have another device – exact the same model – with the bootloader intact. So you:

1. put an SD card into the intact device and use Odin's T-Flash option to write (copy) the bootloader to the SD card


2. put the very same SD card into the broken device, which now can boot from the card

(booting from the card must be supported and sometimes requires specific additional hardware, a so-called USB-JIG-plug).