## Introduction

In addition to dimensions, defining sketch entities relations is very important. It can later save you time in dimensioning (for instance if you have equal line you would only need to define a length once) and also help you to “completely define” your sketch – preventing unexpected problems when changing dimensions and rebuilding the part.

## Relations overview

The relations are of several types:

- Single line relations
- Line to point
- Point to Arc
- Line to line
- Line to arc or circle (here and further, circles are considered as arcs.)
- Arc to arc

Other useful relations

## Single Line relations

Horizontal – line is parallel to construction plane X axis

Vertical – line is parallel to construction plane Y axis

## Point-to-Line relations

Coincident – the point lies on the line or its continuation

Mid-point – the point lies exactly in the middle of the line

## Point-to-Arc relations

Coincident – the point lies on the arc/circle

Concentric – the point lies in the center of the arc/circle

Mid-point – the point lies on the line that passes through line center and middle point.

## Line-to-Line relations

Equal – two lines are of equal length

Parallel – two lines are parallel

Perpendicular – two lines are perpendicular

Colinear – two lines lie on the same “virtual line”

## Line-to-Arc relations

Tangent – the line (or its continuation are tangent to the arc/circle

## Arc-to-Arc relations

Equal – the arcs (or circles) are of equal radius – but not length

Concentric – the center point of the arcs (or circles) are coincident

Tangent – the arc is tangent to another line or circle

Coradial – the arcs lie on the same “virtual” circle.

## Other useful options

- Fix – at any time you can decide that certain sketch entity would not change when you are moving/changing other entities. To do that – select the entity and press “Fix. The selected line/arc will become black – as it cannot change and is now “completely defined”.
- For construction – you can define sketch entity to sere only for sketch definition purposes. The Cut/Extrude feature will ignore it – but it can be helpful to completely defining your sketch.
- Infinite Length – sometimes you would like to set the line as infinite length – and define certain sketch entities relative to it (for instance – angles)– this would of course be the construction line. You actually have 2 unlimited lines present on every sketch – the X and Y axis of the construction plane.