# Sketch Constraints

Sketch constraints apply geometric relationships such as tangency and perpendicularity to sketch curves.

As you create geometry, many sketch constraints are automatically applied. For instance, if you draw a line that is nearly horizontal, a horizontal constraint will be created on that line automatically, making it precisely horizontal for you. When you modify a sketch, the constraints ensure that the intended relationships between the sketch entities remain intact. This behavior can be disabled in the Preferences dialog, which can also be used to modify the default angle measurements for certain constraints.

## Apply a Sketch Constraint

Apply a sketch constraint to geometry to ensure that the intended relationships between sketch entities remain intact.

Constraint | Description |
---|---|

Fixed |
Constrain a sketch point, line, or curve so that it
maintains a fixed position relative to adjacent sketch
curves. (The object itself is not fixed in 3D space. You can
still move it by dragging.) Points, lines, circles, and arcs can all be fixed. The edges of rectangles are separate entities and can be fixed independently. |

Horizontal |
Position line segments horizontally with respect to the sketch plane. |

Vertical |
Position line segments vertically with respect to the sketch plane. |

Collinear |
Align two or more line segments. |

Parallel |
Position two line segments so they are parallel. |

Perpendicular |
Position two line segments so they are perpendicular. |

Tangent |
Position a line segment so that it is tangent to an arc. |

Concentric |
Align two or more circles so they are concentric. |

## Delete Sketch Constraints

Delete sketch constraints to allow more freedom to create free-form objects.