Kid's ASL sign for basement

Definition: the floor of a building partly or entirely below ground level.

Phonological study: I can see that the toddler Juli at age 1;11 tried to control both of her hands, not to move both hands but she did accomplish especially when not being self-conscious.

The handshapes of both hands are unmarked, two of the five unmarked handshapes ("A" in active hand and "5" in passive hand).