Выражение встречается в следующем контексте:
I. For nylon covers, tighten fasteners until "snug tight" only.

II. Здесь же, в Мультитране, нашла ещё контекст с этим выражением, но без перевода (пункты 3 и 8):
Part turn tightening
1 Line up holes with drift pins to maintain dimensions and plumbness of the structure.
2 Fit bolts in remaining holes. Use taper washers if surface slope exceeds 3° and use flat washers under the rotating component.
3 Tighten all bolts to snug tight position, progressing systematically from the most rigid part of the joint to the free edges.
4 On large joints take a second run to check all bolts are snug tight.
5 Match mark installed nuts and bolts using a punch to show that snug tightening is complete. These marks can then be used for final tightening and inspection.
6 Complete tightening using the part turn method according to the table on page 56. Tightening should proceed systematically from the most rigid part of the joint to its free edges. Wrench sockets should be marked at
positions 180° apart to guide the operator in tightening.
7 Knock out drift pins, replace with bolts.
8 Bring these bolts to snug tight position as in step 3, match mark as in step 5 and complete tightening as in step 6.
9 Mark joint to indicate tightening has been completed. One method is to draw lines with crayon between each bolt head forming a squared pattern.

Заранее спасибо