I was just wondering. Do you have a particular item or tool which you use all the time but which was never designed for garden use? I've got several, but 3 of my favourites are .. An old TV table on casters which for most of the time lives in the greenhouse, but with a slightly bigger top screwed onto the original, (and a 'lip' around the edge purely for finesse) it's brilliant for moving loads of plants at once especially in and out of the greenhouse during the hardening off period. The second is a small, old computer desk. The top gets used as a 'potting bench', the other shelves for storing pots and odds and ends. When not used thus, it doubles as a 'half-way house' for plants waiting to go in the ground and, when surrounded by some polythene or bubble-wrap, a moveable cold frame. It even had a short spell as a mini greenhouse and a display stand for some trailing fuchsia. The third is/was one of those 3-fold indoor clothes airers (somewhat bent out of shape by a 60lb retriever blundering into it full tilt!). By judicious use of a junior hacksaw, I reduced one 48" high airer to 3 x 16" high 'triangular' plant supports.
I've got a sack truck. I bought it principally for moving my jukeboxes as they weigh over 300lb. But they're ideal for moving "trees in big pots" and anything really heavy, where using a normal barrow is dangerous as things can be "top heavy." It was only about twenty quid in B&Q and has big blow-up rubber tyres.
I have a Wheelie bin for a water butt, a meat clever for super neat cuttings and cat food foil containers for plant labels,
A brickie's trowel, so old and well used that the end has worn down to a smooth curve. The half a dozen trowels i own get left in the shed while this one is used all the time. Good for planting, weeding ( used like a hoe), digging up carrots and parsnips. It gets left out in the garden in all weathers, no sign of rust but it's now on it's third home-made handle.
