---
title: Rail
order: 3
---

A section swept along a path of points anywhere in 3D. The section is a star, a polygon, a gear, a flower, a ratchet or a line you draw. Each point scales the section, and the Rail can twist from its first point to its last. Open ends are flat.

![a star Rail along an S path, twisted towards its end](../../assets/rail.webp)

## Settings

![the SDF panel of a star Rail](../../assets/rail-panel.webp)

| Setting | Default | Range | What it does |
|---|---|---|---|
| **Radius** | `0.2` | > 0 (soft 5) | The section's outer radius. Each point's **Radius** multiplies it |
| **Shape** | *Polygon* | see below | The section |
| **Sides** | `7` | 1 – 64 (soft 24) | How many lobes go round the path |
| **Inner** | `0.5` | 0 – 1 | Where the valleys between the lobes sit, as a share of **Radius**. Not shown for *Polygon* |
| **Twist Start** | `0°` | soft −360° – 360° | The section's turn at the first point |
| **Twist End** | `0°` | soft −360° – 360° | The section's turn at the last point. The Rail turns evenly between the two, by length |
| **Mirror** *(Custom)* | on | | The drawn line is half a lobe, mirrored into a whole one. Off, it is the whole lobe and steps back along a radius, like a ratchet tooth |
| **Section** *(Custom)* | | | The Curve data-block that holds the drawn line, with **New** and `X` to clear it, then Blender's curve profile widget |
| **Cyclic** | off | | Closes the path into a loop |
| **Points** | | 2 points or more | The point list and the active point's rows, see [Points](points.md#the-points-panel). A Rail's rows show each point's **Radius** |

The rows every shape has are in [Properties Panels](../../interface/panels.md#rows-every-shape-has). A new Rail is a polygon of seven sides.

## Shape

![Star, Polygon, Gear, Flower, Ratchet](../../assets/rail-sections.webp)

| Shape | Section |
|---|---|
| **Star** | **Sides** points, its valleys at **Inner** |
| **Polygon** | A regular polygon of **Sides** sides (three at least) |
| **Gear** | Square teeth, cut down to **Inner** |
| **Flower** | Round petals, meeting at **Inner** |
| **Ratchet** | Saw teeth that lean one way, back to **Inner** (two at least) |
| **Custom** | The line drawn in the **Section** widget: left to right is across one lobe, bottom to top from **Inner** to **Radius**. Clearing the Section makes it a star again |

![a Custom section: Mirror, the Section data-block and the curve profile widget](../../assets/rail-custom-section.webp)

A drawn line too detailed for the shape is simplified, and the panel says *"Section simplified: a lobe keeps 24 points of its line"*. The Section is saved with the file and can be shared between Rails.

## Rounding

**Rounding** rounds the corners of the section all along the Rail, and the rims of its flat ends. `B`, the Rounding arc and the right-click menu's *Rounding Profiles* and **Rounding** set it.

## Twist dot

In [Edit mode](../../interface/edit-mode.md), with the first or last point selected, a white dot just outside its ring sets that end's twist: drag it round the path. `Ctrl` snaps to 15° (`Ctrl + Shift`: 1°), `Shift` is precision.

![the white twist dot dragged round, with Ctrl held](../../assets/rail-twist.webp)

A selected point's ring sets its **Radius**, as on a [Tube](tube.md#radius-ring). The dots, rounding handles, point handles and add dots are on [Points](points.md#the-handles-in-the-viewport).

## Right-click menu

The right-click menu (and the `Q` pie's West wedge) drags **Radius**, **Sides** and **Inner**. Drag **Sides** away from the shape for more (one per 24 pixels), or step it with the mouse wheel or `Up` / `Down`. **Rail Shapes** picks the section by name, **Path** sets *Open* or *Cyclic*.

## Redo panel

After adding, the redo panel (`F9`) has **Radius** (default `0.2`) and **Align** (*World*, *View*, *3D Cursor*).

## Limits and known issues

> [!warning]
> The SDF panel has no **Rounding** row for a Rail. Set it with `B`, the Rounding arc or the right-click menu.

A Rail holds about 85 Smooth or Corner points. Past that, adding a point reports *"No room for another point"*.

## See also

- [Tube](tube.md): the same path with a round section
- [Points](points.md)