It is not mandatory to hold a qualification to start the Sheet Metal Trades Worker skills assessment. You are required to EITHER hold your completed apprenticeship papers as a Sheet Metal Trades Worker and 3 years of paid work experience pre or post qualification. For example, if you are from the UK you would need your NVQ3 and 3 years of paid work experience.
If you have NO NV3, then you are required to have a minimum of 5 years paid work experience completing sheet metal tasks. It is common for clients to be assessed without holding any formal training or qualification so we use your 5 years of paid work experience as proof.