# Keeping a thin layer

A graded block with a designed thin first layer, smoothed unprotected and with that layer kept by `KeepLayer`.

```{include} _generated/thin_layer.viewer.inc
```

```{include} _generated/thin_layer.svg.inc
```

## Key points

```{include} _generated/thin_layer.keypoints.inc
```

## The numbers

Check a layer by its thickness: the scaled Jacobian reads 1 for a box-shaped hex of any aspect ratio.

```{include} _generated/thin_layer.table.inc
```

Run `python examples/smoother/hex/04_thin_layer.py` to reproduce; it prints these numbers.