Size it for the birds and for your arms
A chicken tractor fails in two directions: too small, and the hens scalp the ground bare and crowd at night; too big, and nobody moves it, which defeats the entire idea. A fair planning figure is around ten square feet of floor per standard hen, in a rectangle long enough that the covered end and the open run both earn their space. The real limit is weight. If one person cannot lift the handle end and walk the pen forward on a damp morning, the tractor will sit still, the grass under it will die, and the flock will end up living on the very patch the design was meant to avoid. Build the size your arms can keep moving, and keep the flock to suit it.
Frame, mesh and the covered end
Light timber or bent conduit keeps the frame manageable; what matters is rigidity, because a pen that racks and twists will open gaps at the corners as it moves. Skin it in welded mesh with a gauge a dog cannot tear — chicken wire keeps hens in but keeps very little out, and on a tractor there is no coop door between the flock and the night. The covered end needs a weatherproof roof, a roost bar and a nest box the hens can reach without leaving the pen, plus a hatch you can open from outside for egg collection and cleaning. Shade cloth over part of the open run keeps the flock comfortable when the tractor sits in full sun at midday.
Wheels, handles and the sealed ground line
The classic arrangement — wheels at one end, handles at the other — works because it lifts like a barrow and the far end drags just enough to stay grounded. Set the wheels so the frame clears the ground only while you are actually moving it; a tractor that rides high at rest invites something to duck underneath. Walk the perimeter of every fresh siting with your eyes on the ground line. Grass hides dips, and a gap you could slide a hand under is a door to a fox or a farm dog. A loose skirt of mesh pegged flat around the base closes those dips on uneven ground and lifts away when it is time to move.
The daily move, done the same way every time
Move first thing, before the flock gets restless, and move onto the next strip of fresh grass in a planned direction so the whole field gets worked evenly rather than one corner getting hammered. Lift the handle end and walk slowly — the hens stroll along inside at your pace, and a slow move means no feet are caught under the dragging edge. Move the full length of the pen each day so the flock always lands on ground that has rested since its last visit. Bring the waterer with you, not after you; hens drink heavily in the morning. On ground the tractor has just left, you are reading the report card: evenly nibbled grass and scattered droppings mean the stocking is right, while a bare, sour patch means the moves need to be longer or the flock smaller.
Making the move a habit that survives busy weeks
The tractor system only pays when the move happens every single day, including the wet ones and the rushed ones. Keep the route planned a week ahead so a tired morning involves no decisions, and keep the waterer's spare and the peg bag with the tractor itself. On KinsLe Care Teams the daily shift can be set as a standing morning duty for the flock, and the timestamp on each completed move shows at a glance that the birds are on fresh ground even on days you are away.