If an adult had been the beneficiary of each of these trusts, of course the gifts *110 would not have been of future interests, since then (under Article Third) each such adult at any time could have demanded payment of income and (under Article Eleventh) of the corpus. 2 But here we have the following differentiating facts: (1) None of the children could himself make such a demand; he could do so only through a guardian. (2) The donor testified as follows: He had set up the trusts for the express purpose of teaching the three children how to invest their own money; his attorney had suggested naming a guardian in the instrument, but the donor had objected, because a guardian would be limited by law in what use he could make of the income on the children’s behalf, and would be unable to allow them free play in the pecuniary education the donor wanted them to have. (3) No guardian was appointed during the period of three years from the creation of the trusts to the date of the trial here, although in New York, consent of the donor,' the father, would not apparently have been necessary to the appointment of a guardian. 3 On these facts the Tax Court concluded, and we agree, that only future interests were conveyed at the time the trusts were set up.

It is urged that neither the Tax Court nor we may properly consider these items, since they involve restrictions not contained in the trust instrument. Cf. Kieckhefer v. Commissioner, 7 Cir., 189 F.2d 118, 122. But in Fondren v. Commissioner, 324 U.S. 18, 24, 65 S.Ct. 499, 89 L.Ed. 668, and Commissioner v. Disston, 325 U.S. 442, 449, 65 S.Ct. 1328, 89 L.Ed. 1720, the Supreme Court, in determining the nature of the rights conferred by the trust instruments, took account of “surrounding circumstances”; the Court, in reaching its determinations, did not irrevocably lock itself inside the “four corners” of the writings but held that the key might lie outside. Were this not the rule, a donor could make gifts which on paper were 100% present but in practice were 100% future.

The Court of Appeals, in the Kieckhefer case, expressed the fear that no gift to a minor would be tax-free if the child’s right at once to enjoy the fruits of the gift constituted the sole test of a present interest, since (it was said) the child’s guardian or parent will always exercise control of some sort over the disposition of the child’s property, so that only if the-child’s rights were those of “a boy to his top” or a “girl to her doll” would the gift be tax-free. 4 We believe this view under-estimates the traditional judicial knack of line-drawing. If here, for instance, the donor had, in the instrument, appointed a guardian to exercise the children’s election rights, or indeed even if a next best friend of the children, had successfully petitioned for one at the time the trust first was set up, the result might very well be different. 5 Then there would have been someone who, on the children’s behalf, could have made an effective demand for income or corpus on the trustees under *111 Articles Third and Eleventh. Here, there was no one who could exercise their election rights for them; consequently they acquired only “future interests,” not subject to immediate capture.

Affirmed.