All straight lines, a vee-shaped arrangement of two 30×30 shs, each roughly 2m long, joined at one end, 1m (?) apart at the other. The 1m gap is spanned by a 40×40 angle approximately 1.3m long. This is the axle, which overhangs the square sections at either end by (say) 150mm. Into the angle is welded a short length (225mm?) of 25mm round tube, one at each end. The wheels slot onto these.
At the other end of the vee is the handle, plus a short section of tube mounted vertically to hold a jockey wheel.
Slightly bizarrely there is a dimensioned sketch of a fairly similar trolley on the Trident website, I’ve just noticed.