This summary is not the rule. The rule text controls.
This rule protects people accused of crimes in two important ways. First, no one can be forced to testify against themselves in a criminal case. This means a defendant has the right to stay silent and cannot be made to give evidence that would help convict them.
Second, this rule limits how much a person can be restrained before they're actually convicted of anything. Since they're still presumed innocent, the only restraint allowed is what's needed to keep them in custody until their case is decided. Officials can't add extra punishment or restrictions beyond what's necessary for basic detention.
The rule also makes one thing very clear: a defendant can never be put on trial in front of a jury while wearing chains or shackles. This matters because seeing a defendant in restraints could make jurors assume they're dangerous or guilty before they've even heard the evidence. The law wants juries to judge the case fairly, without that kind of unfair influence.