Firstly clear the polytunnel footprint of debris and vegetation.

Next, position the first two foundation tubes the correct distance apart e.g. 10ft apart for a 10ft wide polytunnel. These are marked ‘A’ and ‘B’ in the above diagram.

Secure a tight string-line between the two foundation tubes and mark the 120cm (or 4ft/8ft) position, labelled ‘D’ in the diagram.  A small cable tie or wire twist is ideal for this as it can be moved if required. 

Connect a second length of string to the foundation tubes marked ‘B’ and ‘C’. At this stage, ‘C’ is not secured into position. Ensure the string-line is tight and mark the 90cm point (or 3ft/6ft), labelled ‘E’. 

Now measure the distance between ‘D’ and ‘E’, this should be 150cm (or 5ft/10ft).  If not, then reposition foundation tube ‘C’ (with the tensioned string-line still attached) by moving it either to the right or the left until the distance between ‘D’ and ‘E’ is correct. 

Foundation tube ‘F’ should now be pushed into the ground, if positioned the correct distance from ‘A’ and ‘C’ it should be in the correct position.  

Once you’re happy that your corner foundations tubes are square and in the correct position you can screw them all into the required depth.

As a final check, measure diagonally from corner to corner, these two measurements should be the same. If not then repeat the 3:4:5 triangle method until they are.

Once the four corner foundation tubes are in place the intermediate foundation tubes can then be positioned.

These should be spaced at 5ft (1.52m) or 6ft (1.83m) along the length, depending upon the hoop spacing option you have chosen.