What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
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We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Unfortunately, you cannot delete the "Last Name" field in the full name quick tools. You can hide is using custom CSS if you like.
I can see on your form that you are not using the "Full Name" under "Quick Tools" anymore. I can now see that you are using a regular text box to capture the name.
Hope that helps. Thank you.