The intermediate bar of the device is formed tiltable and length adjustable.

The planting heads are attached to the ends of the intermediate bar by hinges.

The structure of the device enables to adjust the mutual distance of the planting heads and to tilt them in relation to the intermediate bar.

(1) Every guardrail shall consist of a top rail, intermediate rail and toeboard, and be capable of resisting any load likely to be applied to it.

For playing, the intermediate bar is held by the musician to prevent the instrument's oscillation.

A structure comprising a combination of a plurality of retention tool bodies and spacer members is interposed and aligned between clamp frames (17A, 17B) with a bar member (18) therebetween.

A control system comprising two fixed beams (15, 16) and an intermediate beam (17), being connected with the fixed beams by means of chain links (22, 23), is preferred.