Constraints remove degrees of freedom between two selected components, positioning them relative to one another. As you add subsequent parts, you add constraints to position the new parts relative to the other assembled parts.

When you add the first part to a new assembly the part position is fixed, with the part origin coincident with the assembly origin.

When you add the next part and constrain it to the first part, the new part connects to the first part according to the type of constraint applied.

As you add subsequent parts, you add constraints to position the new parts relative to the other assembled parts.

Use the Connect Component function. This function can be accessed by the icon, or by selecting Assembly / Connect Component from the main menu.

When you select Connect Component, the Connect Component Feature Guide is displayed. This guide will prompt you to select the component entities to be connected.

Once you have selected the component entities, you are prompted to select constraints. The only constraints that are available are those that are valid for the component entities selected. Constraints that are not valid for the selected component entities are grayed out. For example:

In certain cases, you can use Alignments to specify the connect solution required.
Rotational constraints are possible only if you position a component specific UCS (User Coordinate System) to another component specific UCS.

There are two kinds of constraints, translational and rotational.

Each connect constraint is valid for a specific type of geometry. Constraints that are not valid for the selected component entities are not available.

Translational constraints have to be defined no matter which component entities are selected - edges, faces, vertices or UCSs. There are two kinds of translational constraints: Connect Relations and Alignments.

Rotational constraints are possible (as an optional step) only if you position a component specific UCS (User Coordinate System) to another component specific UCS.