how does this device secured to hold its height so it does not slump to you lap or something?

Rows of thick bolt screws on metal racks. It's legit sturdy. Had mine for a while now and no complaints, but for the price you can almost get a desk with a tray built in, so there's that to consider.

Questions & Answers: KT1 Ergonomic Keyboard Tray Under Desk - Under Desk Keyboard Tray Slide Out with Adjustable Height and Tilt - Easy to Slide and Swivel 360 Degree - Keyboard Drawer with Adjustable Mouse Pad

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KT1 Ergonomic Keyboard Tray Under Desk - Under Desk Keyboard Tray Slide Out with Adjustable Height and Tilt - Easy to Slide and Swivel 360 Degree - Keyboard Drawer with Adjustable Mouse Pad

ERGONOMIC KEYBOARD TRAY - Raise, tilt, swivel & slide keyboards to the perfect position with this ergonomic keyboard tray under desk slide.
ADJUSTABLE HEIGHT - The desk keyboard tray slide out (4.5 below to desk height) allows you to quickly position keyboards at elbow-height and easily create proper separation between monitors & keyboards.
ADJUSTABLE TILT - Type with a neutral or negative wrist angle and quickly change your typing posture throughout the day with a fast, intuitive tilt adjustment with our keyboard tray under desk adjustable height.
SWIVEL & SLIDE - Our keyboard tray under desk adjustable height swivels 360 and slides completely under your desk without greasy bearings. Its fast, simple & intuitive to adjust your keyboards position
Built to Last - Invest in durability and stability with our commercial-grade keyboard desk mount.

$86^.42 –