Below is the DDB (Digital Dictionary of Buddhism) entry for 結制:
(http://buddhism-dict.net/cgi-bin/xpr-ddb.pl?q=結制)

The three-month period of retreat in summer and winter followed in Chan monasteries, during which monks were bound to remain in the monastery for the duration. Contrasted with the ‘slackened rule,’ 解制，the free seasons of spring and fall, when monks were free to travel. Cf. 安居 and 結夏. 〔緇門警訓 T 2023.48.1042b9〕 [Robert Buswell]

結制 is an interesting example of a particular kind of two-character word in Chinese. The two characters have similar meanings, and their combination emphasizes the shared meaning.

結 (gyeol) means “knot” or “tied up”. 制 (je) means “control” or “regulate”. During the three-month retreat period every minute of every day is tightly controlled. There are stories of some temples where the meditation hall only has one door, and that door locks from the outside, and is kept locked during the entire 90-day retreat period. I have personally seen meditation halls where paper has been placed over the windows so that retreatants cannot see outside.

So “Kyol Che” doesn’t literally mean “tight dharma”. But that does give a good feel for what Kyol Che is. The literal meaning is “tightly controlled”.

Also, the DDB entry (quoted above) very helpfully mentions the closely related term 解制 (hae je), which literally means “loosely controlled”. This is the