> ## Documentation Index > Fetch the complete documentation index at: https://cal.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Managing booking fields > Prefilling and / or making them read-only. ## Prefilling default booking fields If you want to pre-fill name and email fields you can pass them to the Booker atom's defaultFormValues prop: ```js theme={null} ``` which will look like:

## Prefilling custom booking fields We created an event type for managed user with custom text and select fields. Name and email fields are created by default. Here is the request:

That looks in booker like:

Let's say you want that when someone is trying to book one of your managed users that the booking fields should be pre-filled with some data. We see that one of the booking fields has slug `coding-language` and the other `help-with`. To pre-fill them you pass their slugs and values to the Booker atom's defaultFormValues prop: ```js theme={null} ``` which now will populate the booking fields:

## Making pre-filled fields read-only `disableOnPrefill` booking field property controls whether or not to make a booking field read only if we pass its value in the defaultFormValues prop. Here is an example request where we create an event type with one booking field with "disableOnPrefill": true and the other with "disableOnPrefill": false:

If we pass their values to the Booker atom: ```js theme={null} ``` then here is how it will look like in the Booker. The "What language will we peer code in" text field is read only: