Tuning Slide

Richard stood with his eyes fixed upon his music, expecting to see his companion alter the tuning-slide of his flute; but the man waited, with ❋ George Manville Fenn (1870)

"I'll come too," said Anson, and he began to rapidly unscrew his flute, but so hurriedly that in place of separating the top joint from the next he pulled it open at the tuning-slide, changed colour, and swung himself round so as to turn his back to his companions, keeping in that position till his instrument was properly separated and replaced in its case, whose lid he closed, and then turned the key. ❋ George Manville Fenn (1870)

But Ingleborough lowered the flute, held it in both hands, and drew it apart at the tuning-slide, held it sidewise, and then unscrewed the top plug, showing an opening, out of which he shook a magnificent gem of great size and perfect make. ❋ George Manville Fenn (1870)

Whistles in this category are likely to be made of metal or plastic tubing, with a tuning-slide head.

I'd not interfere with the tuning-slide: it's quite correct. " ❋ George Manville Fenn (1870)