Big O said:
I may have not been very clear.
To get maximum points you need to have 4 years of experience in any of the 29 NOCs.
If you have 4 years of continuous work out of which only 1 year was spent in one of the 29 NOCs then you will be awarded points corresponding to 1 year only.
Ok, let's read the guide together
here http://www.cic.gc.ca/english/information/applications/guides/EG72.asp
it says
Am I eligible?
Your application will be placed into processing if…
you have at least one year of continuous full time or equivalent paid
work experience in the last ten years
in at least one of the occupational categories identified in the Ministerial Instructions.
Note: The list of occupations can be found on our website at: www.cic.gc.ca/english/immigrate/skilled/
apply-who-instructions.asp
I am eligible, what is the next step?
Once you have determined that you are eligible for processing, you must also
meet the minimal requirements for Federal Skilled Workers, meet the minimum funds requirement and obtain sufficient points under the selection factors.
What are the minimal requirements?
All applicants must meet the following minimal requirements to apply as a skilled worker:
You must have at least one year of continuous full-time, paid work experience or the equivalent in part-time continuous employment
You must have had this experience within the last 10 years
Your work experience must be Skill Type 0 (managerial occupations) or Skill Level A (professional occupations) or B (technical occupations and skilled trades) on the Canadian National Occupation Classification (NOC)
And further again
Work experience
(maximum of 21 points)
You will earn points for the number of years you have spent in full-time (37.5 hours per week), paid work.
Minimum work experience requirements
You must meet the following minimum work experience requirements to be eligible to apply as a skilled worker:
You must have at least one year of full-time, paid work experience or the equivalent in part-time employment.
Your work experience must be in an occupation of Skill Type 0, or Skill Level A or B of the Canadian National Occupation Classification (NOC). See below for instructions on determining the NOC category for your work experience.
You must have had this experience within the last 10 years.