﻿ Getting Started Tutorials - MechDesigner > Tutorial 4: From Sketch-Elements to Extrusions > Step 4.1: Sketch-Loops and Merged-Points

# Step 4.1: Sketch-Loops and Merged-Points

## Sketch-Loops.

### Key Terminology

Sketch-Loop: the derived name for a closed chain of sketch-elements.

Merged-Points: two Points* that are merged into one Point.

* start-Point or end-Point of each sketch-element.

### Objectives:

This topic has a video of example sketch-loops in the Part-Editor.

Add sketch-elements, end-to-end, to form a single, continuous loop - see exceptions below.

Add Constraints to the sketch-elements. Constraints are not required, but it is good practice.

We can add a Profile to a sketch-loop. We can also add a Hole to a sketch-loop.

EXCEPTIONS

With sketch-loop:

three(3) or more(+3) Points cannot be merged to one Point – this is a Branch Point

sketch-elements cannot cross over each other - this is a Figure-of-Eight

sketch-elements cannot touch each other (other than their merged-Points) - this is Zero-Thickness

### Example Sketch-Loops

 1: A Circle The simplest sketch-loop. Used for a Cam-Follower Roller. See Also: Cam-Follower 2: Lines General polygon. 3: Lines and Arcs General shape. 4: Arcs and Arcs General free-form shape Tutorial 4: Add Sketch-Loops