Check the horizontal backing rails on the rear of the panel. Ultra Heavy Duty panels have one additional 75 x 32mm backing rail compared with the Standard panel at the same height.
The most reliable identifying feature is the number of horizontal backing rails. At the same height, an Ultra Heavy Duty East Coast Fencing closeboard panel has one more 75 x 32mm rail than the Standard version.
- 3ft, 4ft and 5ft: Standard uses 3 rails; Ultra Heavy Duty uses 4.
- 5ft 6in and 6ft: Standard uses 4 rails; Ultra Heavy Duty uses 5.
Both versions use the same basic closeboard construction of 18 overlapping feather edge boards and remain 1830mm wide and approximately 45mm deep at corresponding heights. The front face can therefore look very similar.
For example, the 6ft Standard panel has four backing rails, while the 6ft Ultra Heavy Duty panel has five.
Pressure-treatment colour is not an identifier. Brown and green/natural versions use the same rail specification when the height and Standard or Ultra construction are otherwise equivalent.
If you are identifying an existing panel for replacement, check its height first and then count the backing rails. The complete range can be compared under closeboard fence panels.