In graphite, the weak covalent bonds that allow atoms to slip and slide are the van der Waals forces between the layers of carbon atoms.

Here's a breakdown:

* Strong Covalent Bonds within Layers: Graphite's structure consists of layers of carbon atoms arranged in a hexagonal lattice. Within each layer, the carbon atoms are linked by strong covalent bonds. This strong bonding creates a very stable and rigid structure.

* Weak Van der Waals Forces between Layers: The layers of carbon atoms are held together by relatively weak van der Waals forces. These forces arise from temporary fluctuations in electron distribution around the atoms.

* Slippage and Sliding: Because the van der Waals forces are weak, the layers of carbon atoms can easily slide over one another. This is what makes graphite soft, slippery, and an excellent lubricant.

In short, the weak van der Waals forces between layers allow the layers to easily slide past each other, giving graphite its unique properties.