Symbol 6035A from IEC 60417 - Title/Meaning: Press and hold; long push Function/description: [To provide information for the specific control that shall be pushed in, and held continuously, until it completes the intended operation.This symbol should be used in combination with supplementary text to explain the corresponding function.]
Additional information: 
See also alternative symbol 6035B.
Own work using: iso.org/obp/graphics/grs/37509183-4726-4671-ba7f-acbb119b53fa 200.png
Vectorization:  Mrmw