How to make a table that has read only cells and editable cells?

I am tying to make a table that looks like this:

Product Name / Size / Item# / Quantity

Name1          / Size1 / Item1 / fillable by user

The only cells I want the used to be able to change is the fillable by user portion.

Basically, you only need to allow users to fill the Quantity. But I'm not sure if you are planning to have a different data on each row for the first 3 columns. I think that's how you want to set it up, based on the sample data with numbers.

Please try checking our configurable list widget: https://www.jotform.com/help/282-How-to-Set-Up-the-Configurable-List-Widget. 

Let us know if you need help with this.

Yes, I would like to have different data on every line.  Quantity is the only field that the user will fill out.  

I see. The configurable list widget can't do it. But you are currently using the Spreadsheet widget. That should work. To disable the cell, you need to define it in the Read Only settings. Here's an example on how you should disable the inputs:

Here's my test form: https://form.jotform.com/60953901608963.