Aqui está o meu código:

$("#product1 :checkbox").click(function(){
    $(this)
        .closest('tr') // Find the parent row.
            .find(":input[type='text']") // Find text elements in that row.
                .attr('disabled',false).toggleClass('disabled') // Enable them.
                .end() // Go back to the row.
            .siblings() // Get its siblings
                .find(":input[type='text']") // Find text elements in those rows.
                .attr('disabled',true).removeClass('disabled'); // Disable them.
});

Como alternar.attr('disabled',false);?

Não consigo encontrá-lo no Google.