> For the complete documentation index, see [llms.txt](https://jonny-wamsley.gitbook.io/the-ultimate-guide-to-keyboard-layers/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jonny-wamsley.gitbook.io/the-ultimate-guide-to-keyboard-layers/ch-3-layer-activators/3.5-dual-layers.md).

# 3.5 Dual Layers

A dual activated layer also known as tap-hold activator is a combination between a normal key and a momentary layer. That is, when tapped, the key will output a keycode, but when held, will activate a momentary layer.

At first I used momentary layers and normal keys on my thumb keys. Later, I transitioned into using dual layers on all the momentary layers. I have 6 dual key layers and 0 momentary layers as of now.

One problem with dual layers arises when determining when a tap become a hold. If you slowly tap a key, you may activate a layer accidentally and can mess up your expected output. For this reason, there are 2 preference settings to adjust. This is specific to bazecor, the software I use but should have some similarity to [QMK tapping term](https://docs.qmk.fm/#/tap_hold?id=tapping-term).

* Overlap Threshold value: This value determines how long the layer will continue to stay activated after you let go of the layer.
  * If a shift layer is used as a dual function layer, then you want to have a low threshold value, else you will have mistakes like THe with 2 layer values activated instead of one.
  * I like this value at 1 so if I slightly tap a letter key before the dual key in nano seconds, then the layer will still activate. This value should be vary low though to avoid accidental consecutive layer outputs.
* Hold Timeout value: This value determines the delay in the tap press. 
  * If this value is 0 then tap will produce no value. If this value is max, then it will be instant.
  * I like this value at max so when I tap a key it appears instantly.

![My Dual-function key settings in Bazecor](/files/Fi6XaKsZEiXIldQDernX)

Using these settings will take some time to get used to, but ultimately will make you a better and more consistent typist. Key strokes should be swift, and if you are holding down on a key too long, then you will accidentally activate a layer. It may be frustrating at first, but can be easily improved upon in my experience. For practice, I used a typing site called [keybr](https://www.keybr.com/) and under the setting, enabled capitalization to practice my shift and punctuation dual layer keys. A typing lesson below on keybr looks like:

> Coung␣Thire␣The␣Thousant␣She␣Greads␣You␣More␣Eyes␣And␣Ful␣Assed␣Fall␣Can␣That␣Usuade␣Tell␣Who␣Been␣Did␣Every␣Sort␣She␣His␣You

If you are typing COung, THire then you need to lift your dual function key finger up more quickly.

{% hint style="info" %}
There is a concept of home row mods, which use dual keys with letters and layers on the home row. Personally, I find home row mods hard to use because words I am less familiar with I type slower which makes it difficult to find threshold settings that work. I don't think I should slow my typing speed to make home row layers usable.
{% endhint %}