A One Line Input field allows you to force a specific string format. We begin by adding a field on the form edit page: Add Field -> Basic -> One Line Input.

When editing the field select Specific Format under Validation.

Input mask options for one line text field

The format column can be used to specify the mask format we need to enforce.

Commonly used formats:

US Phone: ({000}) {000}-{0000}
Canada Postal Code: {a0a} {0a0}
Social Security: {000}-{00}-{0000}

You can also make your own format using this legend:

0 = allow only 0 - 9
* = allow any character
a = allow only a - z
[] = make character optional
{} = make character required