Guide element especially suitable for solar greenhouses and the like and particularly utilizable for controlled shading

A structural arrangement which is particularly useful in connection with solar greenhouses is provided. Therein is provided a structural member in the form of a hollow bar of elongated form provided with longitudinally extending and parallel track channels having relatively narrow longitudinally extended slot mouths. A shade with a bulbous periphery is engaged in each of the track channels and a guide member is provided which changes the direction of movement of the shade as it exits from the ends of the corresponding track channels. The guide includes tubular extensions which extend into the track channels. The guide furthermore includes arcuate guide channels which are funnel shaped and operate in extension of the tubular extensions. A member operates in conjunction with the tubular extensions to a wall of the afore-mentioned bars for the mounting of the guide.