Our character today is 闸 | 閘, composed of 门 | 門 and 甲, both of which we have learnt. 门 | 門 means door or gate, while 甲 means armor. We can reasonably guess that 闸 means door or gate protected or enforced with armor.
In ancient China, usually such 闸 was normally used either for gate of a fortified city, for example 闸门:
When modern physics was introduced to China, electric switches was translated to 电(electricity)闸, as electricity is one form of current as well.
And we can see from its evolution history that its presentation does not really change from Seal Script till now: (image taken from: http://vividict.com)
|evolution history of 闸|
That is all for 闸 | 閘, it is now our time to enjoy a Chinese calligraphy with 闸 | 閘 inside: