Cable tray hold-down device

A hold-down device for holding a cable tray on a support includes a rigid member having opposite side edges, opposite side margins adjacent respective side edges, and opposite end portions. The member may be placed on the support in a position in which the opposite side margins of the member bear on edges of the support with the member overlying the slot adjacent a flange of the cable tray. The member is constructed and arranged such that it is selectively securable to the support by a threaded fastener either in a clamping position in which one end portion of the member overlies the flange of the cable tray and may clamp the flange of the cable tray thereby to hold the rail in fixed position with respect to the support, or in a non-clamping position in which the opposite end portion of the member overlies the flange of the cable tray but cannot clamp the flange thereby to permit lengthwise thermal expansion and contraction of the rail while still holding the rail on the support. First and second anti-spin structures are provided at respective end portions of the member engageable with the support to prevent rotation of the member relative to the support as the threaded fastener is rotated to secure the member in its clamping or non-clamping position.