Final answer:
The holidays that incorporate both hands in the letter shape representing the first letter of their respective words in ASL are Halloween and Thanksgiving. They require using both hands to create the letter 'H' for Halloween and the letter 'T' for Thanksgiving.
Step-by-step explanation:
The student has asked about two holidays which use both hands in creating the letter shape that is the first letter of the respective words in American Sign Language (ASL). Specifically, the holidays in question are Halloween and Thanksgiving. In ASL, the initial handshape for Halloween involves both hands coming together to form the letter 'H', while the handshape for Thanksgiving starts with both hands making an arc motion in front of the body to form the letter 'T'. Both these sign language gestures use both hands, unlike most other letter gestures in ASL which only use one hand.