What do the chains in the "three estate" cartoon signify?

There was a very famous political cartoon produced in the years immediately prior to the French Revolution that depicted two French noblemen and a bishop sitting on the back of an emaciated, shirtless figure shackled hand and feet with chains. The poor figure having to carry the bloated noblemen and clergy represents the Third Estate (the clergy was the First and the nobles were the Second Estates). His shackles represent the complex system of laws and cultural traditions that "bound" the Third Estate. These included especially the unequal tax codes--a "head" tax that vexed the bourgeoisie, the comfortable middle classes that nevertheless lacked titles and the privileges that went along with them. It also included the gabelle, a tax on salt that affected the poorest Frenchmen (also part of the Third Estate) hardest. Additionally, the Third Estate resented royally granted monopolies that tended to favor nobles over those without titles. So the "chains" that shackle the Third Estate are legal and traditional ones imposed by the so-called ancien régime, the system under the Bourbon monarchs. It was anger at these restrictions, in addition to the fiscal crisis that gripped the country in the late 1780s, that sparked the French Revolution.