Modest clothing means your shoulders, tummy, back and thighs are covered. If you're wearing clothing with words printed on it, its not vulgar or offensive, as you are going into the house of the Lord.
Sometimes we forget about tight clothing. Basically anything that draws attention.
Modest attire means clothing that is not revealing. Think business casual or professional. You will be walking through the Temple and it takes about 45 min of walking, so just wear shoes that you can walk in a little bit.
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