Branding

Branding the mark of the Decepticons into one's structure is more significant than than wearing the Autobrand or the simple inks that humans paint upon themselves. It weaves its way into the body, taking hold of vital circuits until it makes its way the Transformers' very spark. And once the branding is done, it is not easy to remove...

Dreamwave continuity
After sufficient (and painful) modifications to the structure, a newly recruited Decepticon would then be branded with the mark of the Decepticons. Starscream once claimed that it was all part of Megatron's way of controlling them.

Energon
When Megatron defeated Scorponok after his resurrection, he painfully branded the mark of the Decepticons onto the Terrorcon general, as a way to remind him of his power.

Later, after the creation Alpha Quintesson's planets, Megatron rebranded Scorponok, going even further than the last time. After this, he captured Inferno and branded the Autobot, causing a mental battle within Inferno on whether or not he was an Autobot. The dilemma only ended with his death.

Transformers Animated
Once the Constructicons had completed the space bridge, Megatron then initiated them into the ranks of the Decepticons. After the Decepticons recited the oath of loyalty, Megatron then branded them with the Decepticon seal...painfully.